OPINION
LEAVY, Circuit Judge:
This appeal arises out of a district court’s exercise of its discretion to depart upward from the applicable Guideline range in imposing sentence. The court found aggravating circumstances for its upward departure, as required by 18 U.S.C. § 3553(b) and (c). Pursuant to 18 U.S.C. § 3742(e), we must now determine whether the extent of that departure was unreasonable. We have jurisdiction under 18 U.S.C. § 3742(a) and 28 U.S.C. § 1291, and we affirm.
FACTS AND PRIOR PROCEEDINGS
On November 12, 1993, David Tenorio Sabían, a twenty-nine year old native and resident of Guam, was given a live hand grenade by his friend, Jon Russell “Chas” Simpson, and told to throw it inside the headquarters of the local police department in order to create a diversion for Simpson’s robbery of a nearby store. Sabían did not quite follow Simpson’s instructions; instead, he threw the grenade into the police parking lot adjacent to the local Post Office. The grenade bounced off of a car and rolled towards the Post Office where several individuals, including a woman who was nine months pregnant, were standing. Five people were injured in the blast, three of them severely. In addition, several automobiles and the exterior wall of the Post Office were damaged by flying shrapnel.
Sabían pleaded guilty to territorial charges in Guam Superior Court. Pursuant to the terms of his plea agreement, Sabían was to serve ten years in prison, the sentence to run concurrently with any federal sentence which might be imposed. Federal prosecution was then sought in order for Sabían to be able to serve his sentence in a mainland federal penitentiary, where he hoped to receive psychiatric treatment that apparently was unavailable in the island facility. On June 1, 1994, Sabían waived federal indictment and, pursuant to a written agreement, entered a guilty plea to a single-count information charging him with injuring persons by maliciously damaging a Post Office with an explosive in violation of 18 U.S.C. § 844(f).
The government agreed to recommend a sentence of ten years, and both parties to the plea bargain anticipated that the sentence imposed would be based on an adjusted offense level of 21 with a possible upward departure (pursuant to a subsequent motion filed by the government) to no more than level 32. The district court, however, departed upward to an offense level of 37 and imposed the (then) statutory maximum of twenty years’ imprisonment, to be followed by five years of supervised release. In addition, the court ordered Sabían to pay restitution in the amount of $19,928.72, and imposed a $50 special assessment fee. Sabían timely appealed from his sentence.
A panel of this court vacated the sentence, holding that the district court had abused its discretion by failing to gauge the extent of the departure by analogy to other Guideline provisions. See United States v. Sablan, 90 F.3d 362, 365-66 (9th Cir.1996). We granted rehearing en banc. United States v. Sablan, 101 F.3d 618 (9th Cir.1996).
ANALYSIS
I
It is common to say that the Sentencing Reform Act of 1984 (the “Act”), as amended, 18 U.S.C. § 3551 et seq., 28 U.S.C: §§ 991-98, curtailed the broad discretion formerly afforded district judges at sentencing. What is less often noted is that the Act also provided the courts of appeals with limited jurisdiction to review federal sentences where practically no such review had existed before (i.e., with respect to those sentences which fell within the limitations set forth in the governing statutes). See Dorszynski v. United States, 418 U.S. 424, 431, 94 S.Ct. 3042, 3046-47, 41 L.Ed.2d 855 (1974) (“once it is determined that a sentence is within the limitations set forth in the statute under which it is imposed, appellate review is at an end”).
In the several years since the adoption of the Guidelines, most, if not all, of the Circuits developed multi-step approaches to reviewing sentences that involved departures from the Guidelines. See, e.g., United States v. DiazVillafane, 874 F.2d 43, 49 (1st Cir.1989) (3-step analysis); United States v. Palinkas, 938 F.2d 456, 461 (4th Cir.1991) (4-step analysis), judgment vacated on other grounds, 503 U.S. 931, 112 S.Ct. 1464, 117 L.Ed.2d 610 (1992); United States v. Rodriguez, 882 F.2d 1059, 1067 (6th Cir.1989) (3-step analysis); United States v. Gaddy, 909 F.2d 196, 199 (7th Cir.1990) (similar test); United States v. Lang, 898 F.2d 1378, 1379-80 (8th Cir.1990) (similar test); United States v. White, 893 F.2d 276, 277 (10th Cir.1990) (similar test); United States v. Valle, 929 F.2d 629, 631 (11th Cir.1991) (per curiam) (similar test).
Our Circuit was no exception. In United States v. Lira-Barraza, 941 F.2d 745 (9th Cir.1991) (en banc), we rejected a five-step approach to reviewing departures in favor of a more streamlined three-part test, similar to that which had been announced earlier by the First Circuit in Diaz-Villafane. Under Lira-Barraza,
we would first review de novo whether the trial court had legal authority to depart under 18 U.S.C. § 3553(b), which requires the presence of an aggravating circumstance of kind or degree not adequately considered by the Commission in formulating the Guidelines. Id. at 746. Next, we would review for clear error the factual findings upon which the existence of the identified circumstance was based. Id. Fi nally, we would review the extent of the departure from the applicable Guideline range for reasonableness under 18 U.S.C. § 3742(e)(3). Id. at 747.
United States v. Beasley, 90 F.3d 400, 402 (9th Cir.), cert. denied, — U.S. -, 117 S.Ct. 533, 136 L.Ed.2d 418 (1996).
The Supreme Court has now changed all of this. In Koon v. United States, — U.S. -, 116 S.Ct. 2035, 135 L.Ed.2d 392 (1996), the Court noted as a general proposition that “[a] district court’s decision to depart from the Guidelines ... will in most cases be due substantial deference, for it embodies the traditional exercise of discretion by a sentencing court.” Id. at -, 116 S.Ct. at 2046.
Whether a given factor is present to a degree not adequately considered by the Commission, or whether a discouraged factor nonetheless justifies departure because it is present in some unusual or exceptional way, are matters determined in large part by comparison with the facts of other Guidelines cases. District courts have an institutional advantage over appellate courts in making these sorts of determinations, especially as they see so many more Guidelines cases than appellate courts do.
Id. at-, 116 S.Ct. at 2047. In light of these considerations, the Court declared that a unitary abuse of discretion standard was to be used when reviewing departure decisions. Id. at-, 116 S.Ct. at 2047-48.
By ruling as it did, the Court effectively rejected each of the multi-step approaches to reviewing sentencing departures that had been adopted by the various Circuits and “collapsed” the steps into a single inquiry. See United States v. Cali, 87 F.3d 571, 579-80 (1st Cir.1996) (acknowledging that Koon established a unitary abuse of discretion standard for reviewing departure decisions). Accord United States v. Rioux, 97 F.3d 648, 662-63 (2d Cir.1996); United States v. Romualdi, 101 F.3d 971, 973 (3d Cir.1996); United States v. Hairston, 96 F.3d 102, 106 (4th Cir.1996), cert. denied, — U.S. -, 117 S.Ct. 956, 136 L.Ed.2d 843 (1997); United States v. Wells, 101 F.3d 370, 372 (5th Cir.1996); United States v. Jones, 107 F.3d 1147, 1154 n. 6 (6th Cir.1997); United States v. Besler, 86 F.3d 745, 747 (7th Cir.1996); United States v. Field, 110 F.3d 587, 591-92 (8th Cir. Apr.7,1997); United States v. Beasley, 90 F.3d at 402-403; United States v. Lowe, 106 F.3d 1498, 1501 (10th Cir.1997); United States v. Bernal, 90 F.3d 465, 467 (11th Cir.1996) (per curiam); United States v. Dyce, 91 F.3d 1462, 1472 (D.C.Cir.) (Tatel, J., concurring in denial of rehearing and rehearing en banc), cert. denied, — U.S. -, 117 S.Ct. 533, 136 L.Ed.2d 418 (1996). The Court noted, however, that even under this deferential abuse of discretion standard, a “district court by definition abuses its discretion when it makes an error of law.” Koon, — U.S. at-, 116 S.Ct. at 2047.
In light of Koon’s mandate that a unitary abuse of discretion standard governs our review of departure decisions, we conclude that Lira-Barraza has been overruled. See Beasley, 90 F.3d at 403. See also United States v. Ripinsky, 109 F.3d 1436, 1445-46 (9th Cir. Mar.28, 1997) (citing Beasley).
II
To say that departure decisions must be reviewed for an abuse of discretion, however, says nothing about what factors a district court should take into consideration when confronted with the question of whether or not to depart in a particular case. Fortunately, the Supreme Court spelled out just what those factors should be:
[A] sentencing court considering a departure should ask the following questions:
“1) What features of this case, potentially, take it outside the Guidelines’ ‘heartland’ and make of it a special, or unusual, case?
“2) Has the Commission forbidden departures based on those features?
“3) If not, has the Commission encouraged departures based on those features?
“4) If not, has the Commission discouraged departures based on those features?” United States v. Rivera, 994 F.2d 942, 949 (C.A.1 1993).
We agree with this summary. If the special factor is a forbidden factor, the sentencing court cannot use it as a basis for departure. If the special factor is an encouraged factor, the court is authorized to depart if the applicable Guideline does not already take it into account. If the special factor is a discouraged factor, or an encouraged factor already taken into account by the applicable Guideline, the court should depart only if the factor is present to an exceptional degree or in some other way makes the case different from the ordinary case where the factor is present. Cf. ibid. If a factor is unmentioned in the Guidelines, the court must, after considering the “structure and theory of both relevant individual guidelines and the Guidelines taken as a whole,” id., at 949, decide whether it is sufficient to take the case out of the Guideline’s heartland. The court must bear in mind the Commission’s expectation that departures based on grounds not mentioned in the Guidelines will be “highly infrequent.” 1995 U.S.S.G. eh. 1, pt. A.
Koon, — U.S. at-, 116 S.Ct. at 2045.
The district court identified factors which took Sablan’s case out of the “heartland,” and expressly relied on such approved grounds for departure as those listed at U.S.S.G. ch. 5, pt. K, § 2, including “significant physical injury” (§ 5K2.2) and “property damage” (§ 5K2.5). In light of the above, it cannot be said that the district court abused its discretion by deciding to depart from the Guideline range.
Ill
As a final matter, we must determine whether the extent of the district court’s departure was so great as to be unreasonable for purposes of 18 U.S.C. § 3742(f)(2). See Williams v. United States, 503 U.S. 193, 202, 112 S.Ct. 1112, 1120, 117 L.Ed.2d 341 (1992) (if the reviewing court concludes that the decision to depart was not the result of an erroneous interpretation of the Guidelines, it must then determine whether “the resulting sentence [is] an unreasonably high ... departure from the relevant guideline range”). In the absence of such a determination, we must affirm the sentence imposed. See 18 U.S.C. § 3742(f)(3).
The district court identified three reasons for its decision to depart upward: The significant physical injuries suffered by three of the bombing victims, the extent and value of the property damaged in the blast, and the need for greater deterrence than usual because the judge knew that the criminal who had asked Sabían to throw the grenade into the police station had bought at least one more, and the man who had sold it to him might well have more.
There are several other factors besides the — criteria noted, the severe pain and hospitalization. And one of them is that there are also other grenades still out there.
* * *
The justification for this, the upward departure from the prescribed Sentencing Guidelines to the 20-year maximum imprisonment sentence authorized by law is justifiable considering the extent of the physical injury, and the property damage suffered by the victims. Despite the victim’s — or the defendant’s — excuse me — defendant’s characteristics, detonating a grenade is a very serious offense; the -harm placed on other people’s lives and property will not be tolerated.
The court also settled on this point in the Sentencing Guidelines mainly because of the physical injury involved; and secondarily, because of the property damage, and also because it is hoped that there be some deterrence that will be gained, that will be derived as a result of this case.
C.R. # 14 (T.R. of 10/21/94) at 10, 22-23.
The presentence report said:
[T]he defendant met a friend of Simpsons, J.T. Taimanglo. Taimanglo gave Sabían a grenade at Simpson’s home, Taimanglo showed two grenades which Simpson paid a “fiver” for each grenade.
As already noted, the first two factors have been identified by the Sentencing Commission as grounds justifying upward departures. See U.S.S.G. § 5K2.2, p.s. (physical injury) and U.S.S.G. § 5K2.5, p.s. (property damage). The third factor was a permissible ground for departure in this case, because of the special circumstance alluded to by the judge. The Sentencing Commission weighed the need generally to deter damaging government property with explosives or fire, pursuant to the directive that it do so in 28 U.S.C. § 994(c)(6). But the special circumstance of more live grenades known still to be in related criminal hands in the locality was an out of the ordinary circumstance which the district judge could permissibly consider in deciding that more deterrence than usual was necessary.
Here, the court’s principal concern was clearly with the significant injuries suffered by three of the bombing victims. Citing United States v. Singleton, 917 F.2d 411, 413-14 & n. 2 (9th Cir.1990) as guidance for what constitutes a significant injury under U.S.S.G. § 5K2.2, the court discussed the nature and extent of the wounds inflicted by the bomb:
And for the record, Ann C. Mendiola still has shrapnel in her body, still experiences numbness and pain in her bones in the area where the shrapnel remains; and for three weeks after the blast incident she had difficulty sleeping, and she had nightmares about the blast.
Ms. Mildred Isimang was nine months pregnant; she had four shrapnel wounds to her back[;] one on her buttocks, one on her left arm, one near her left ear, two shrapnel wounds in each leg. And she stated that delivering her baby was hell because it was very difficult since she couldn’t he on her back; the labor lasted seven hours which was the longest she had experienced. And she still has shrapnel in her body and experiences numbness and pain where indicated.
Mr. Toves had to have surgery, because of shrapnel injuries to the stomach area. He had the through and through perforation of the ileum, with perforation of the right transverse column, laceration of the omen-tum, and right perineal histoma. And because of his injuries he had to use 300 hours of sick leave to recuperate.
C.R. # 14 (T.R. of 10/21/94) at 6-7.
The district court carefully explained its reasons for departing upward from the Guideline range, and did so on the basis of factors that have been expressly designated by the Sentencing Commission as approved bases for upward departure.
In Lira-Barraza, we relied heavily on the Seventh Circuit’s decision in United States v. Ferra, 900 F.2d 1057 (7th Cir.1990), appeal following remand, 948 F.2d 352 (7th Cir. 1991), as support for the proposition that the extent of an upward departure requires a comparison to analogous Guideline provisions. 941 F.2d at 748-50. In light of Koon, we now reject such a mechanistic approach to determining whether the extent of a district court’s departure was unreasonable, and hold that where, as here, a district court sets out findings justifying the magnitude of its decision to depart and extent of departure from the Guidelines, and that explanation cannot be said to be unreasonable, the sentence imposed must be affirmed.
CONCLUSION
As the Supreme Court has repeatedly noted, “it is not the role of an appellate court to substitute its judgment for that of the sentencing court as to the appropriateness of a particular sentence.” Koon, — U.S. at -, 116 S.Ct. at 2046 (quoting Williams, 503 U.S. at 205, 112 S.Ct. at 1121-22 (in turn quoting Solem v. Helm, 463 U.S. 277, 290 n. 16, 103 S.Ct. 3001, 3009, 77 L.Ed.2d 637 (1983))). Because the extent of the district court’s departure was not unreasonable, we find no abuse of discretion in the sentence imposed. Accordingly, the decision appealed from is
AFFIRMED.
. (b) Application of guidelines in imposing a
sentence. — The court shall impose a sentence of the kind, and within the range, referred to in subsection (a)(4) unless the court finds that there exists an aggravating ... circumstance of a kind, or to a degree, not adequately taken into consideration by the Sentencing Commission in formulating the guidelines that should result in a sentence different from that described. ...
18 U.S.C. § 3553(b) (in relevant part).
(c) Statement of reasons for imposing a sentence. — The court, at the time of sentencing, shall state in open court the reasons for its imposition of the particular sentence, and, if the sentence—
(2)is not of the kind, or is outside the range, described in subsection (a)(4), the specific reason for the imposition of a sentence different from that described.
18 U.S.C. § 3553(c)(2).
. (e) Consideration. — Upon review of the record,
the court of appeals shall determine whether the sentence—
(3)is outside the applicable guideline range, and is unreasonable, having regard for—
(A) the factors to be considered in imposing a sentence, as set forth in chapter 227 of this title; and
(B) the reasons for the imposition of the particular sentence, as stated by the district court pursuant to the provisions of section 3553(c); or
(4)was imposed for an offense for which there is no applicable sentencing guideline and is plainly unreasonable.
18 U.S.C. § 3742(e) (in relevant part).
. At the time of the offense, section 844(f) read, in relevant part, as follows:
Whoever maliciously damages ... by means of an explosive, any building ... in whole or in part owned, possessed, or used by ... the United States ... shall be imprisoned for not more than ten years, or fined not more than $10,000, or both; and if personal injury results shall be imprisoned for not more than twenly years, or fined not more than $20,000, or bothf.]
. Between the time of the offense and sentencing, Congress amended subsection (f) to increase the maximum terms of imprisonment (i.e., from ten years to twenty years for damage to government property, and from twenty years to forty years for resultant injuries to third parties), and the maximum possible fines as well. See Act of Sept. 13, 1994, Pub.L. No. 103-322, § 320106(1), reprinted in 1994 U.S.C.C.A.N. (108 Stat. 2111) at 1801.
. If significant physical injury resulted, the court may increase the sentence above the authorized guideline range. The extent of the increase ordinarily should depend on the extent of the injury, the degree to which it may prove permanent, and the extent to which the injury was intended or knowingly risked. When the victim suffers a major, permanent disability and when such injury was intentionally inflicted, a substantial departure may be appropriate. If the injury is less serious or if the defendant (though criminally negligent) did not knowingly create the risk of harm, a less substantial departure would be indicated. In general, the same considerations apply as in § 5K2.1 [i.e., when death results].
U.S.S.G. § 5K2.2, p.s.
Sablans base offense level of 24 was calculated under U.S.S.G. § 2K1.4(a)(1)(A), because he knowingly created a substantial risk of death or serious bodily injury to third parties by damaging properly with explosives. See id. However, because bodily injury actually resulted, an upward departure was warranted under § 5K2.2. See U.S.S.G. § 2K1.4, comment, (n.l).
. If the offense caused property damage or loss not taken into account within the guidelines, the court may increase the sentence above the authorized guideline range. The extent of the increase ordinarily should depend on the extent to which the harm was intended or knowingly risked and on the extent to which the harm to property is more serious than other harm caused or risked by the conduct relevant to the offense of conviction.
U.S.S.G. §. 5K2.5, p.s.
. (f) Decision and disposition. — If the court of appeals determines that the sentence—
(2) is outside the applicable guideline range and is unreasonable or was imposed for an offense for which there is no applicable sentencing guideline and is plainly unreasonable, it shall state specific reasons for its conclusions and—
(A) if it determines that the sentence is too high and the appeal has been filed under subsection (a), it shall set aside the sentence and remand the case for further sentencing proceedings with such instructions as the court considers appropriate____
18 U.S.C. § 3742(f)(2)(A).
. (f) Decision and disposition. — If the court of appeals determines that the sentence—
(3) is not described in paragraph (1) [i.e., imposed in violation of law or an incorrect application of the Guidelines] or (2) [outside the applicable Guideline range and unreasonable in extent, or plainly unreasonable if "imposed for an offense for which there is no applicable sentencing guideline”], it shall affirm the sentence.
18 U.S.C. § 3742(f)(3) (in relevant part).
. A split panel of the Seventh Circuit recently upheld the rationale of Ferra in the face of Koon. See United States v. Horton, 98 F.3d 313 (7th Cir.1996). We note in passing that the majority in Horton cited to Lira-Barraza as continuing support for the above rule (i.e., that upward departures require comparisons to analogous Guideline provisions), while ignoring such available decisions from this Circuit as Beasley and United States v. Goshea, 94 F.3d 1361, 1365 (9th Cir.1996), both of which declared Lira-Barraza to have been overruled by Koon.
. Our holding should not be interpreted as prohibiting the district courts from considering the possible relevancy of analogous guidelines. See 18 U.S.C. § 3553(b) ("In the absence of an applicable sentencing guideline in the case of an offense other than a petty offense, the court shall also have due regard for the relationship of the sentence imposed to sentences prescribed by guidelines applicable to similar offenses and offenders, and to the applicable policy statements of the Sentencing Commission.”). Such a ruling on our part would effectively amount to a usurpation of the power delegated by Congress to the Sentencing Commission to impose categorical proscriptions against considering certain factors at sentencing. See Koon, -U.S. at-,-, 116 S.Ct. at 2047, 2051. An analysis and explanation by analogy, per Lira-Barraza, may still be a useful way for the district court to determine and explain the extent of departure, but it is not essential.