JUSTICE MARSHALL delivered the opinion of the Court.

The question presented is whether a complaint filed in forma pauperis which fails to state a claim under Federal Rule of Civil Procedure 12(b)(6) is automatically frivolous within the meaning of 28 U.S.C. § 1915(d). The answer, we hold, is no.

I

On October 27, 1986, respondent Harry Williams, Sr., an inmate in the custody of the Indiana Department of Corrections, filed a complaint under 42 U.S.C. § 1983 in the United States District Court for the Southern District of Indiana, naming five Indiana correctional officials as defendants. App. 38. The complaint alleged that, while at the Indiana State Prison, Williams had been diagnosed by a prison doctor as having a small brain tumor which affected his equilibrium. Id., at 40. Because of this condition, the doctor placed Williams for one year on "medical idle status." A medical report Williams attached to the complaint stated that "[i]t is very likely that he will have this condition for some time to come." Id., at 48.

The complaint further alleged that, when Williams was transferred to the Indiana State Reformatory, he notified the reformatory staff about the tumor and about the doctor's recommendation that he not participate in any prison work program. Id., at 41. Despite this notification, reformatory doctors refused to treat the tumor, id., at 40-41, and reformatory officials assigned Williams to do garment manufacturing work, id., at 42. After Williams' equilibrium problems worsened and he refused to continue working, the reformatory disciplinary board responded by transferring him to a less desirable cell house. Id., at 42-43.

The complaint charged that by denying medical treatment, the reformatory officials had violated Williams' rights under the Eighth Amendment, and by transferring him without a hearing, they had violated his rights under the Due Process Clause of the Fourteenth Amendment. Id., at 44. The complaint sought money damages and declaratory and injunctive relief. Id., at 45-46. Along with the complaint, Williams filed a motion to proceed in forma pauperis pursuant to 28 U.S.C. § 1915(a), stating that he had no assets and only prison income. App. 36-37.

The District Court dismissed the complaint sua sponte as frivolous under 28 U.S.C. § 1915(d) on the grounds that Williams had failed to state a claim upon which relief could be granted under Federal Rule of Civil Procedure 12(b)(6). Insofar as Williams claimed deficient medical care, his pleadings did not state a claim of "deliberate indifference to [his] serious medical needs," as prisoners' Eighth Amendment claims must under Estelle v. Gamble, 429 U.S. 97, 104 (1976), but instead described a constitutionally noncognizable instance of medical malpractice. Williams v. Faulkner, Cause No. IP 86-1307-C (SD Ind., Jan. 16, 1987), reprinted at App. 67. Insofar as Williams protested his transfer without a hearing, his pleadings failed to state a due process violation, for a prisoner has no constitutionally protected liberty or property interest in being incarcerated in a particular institution or a particular wing. Id., at 26. The court gave no other reasons for finding the complaint frivolous. On Williams' ensuing motion to vacate the judgment and amend his pleadings, the District Court reached these same conclusions. Williams v. Faulkner, Cause No. IP 86-1307-C (SD Ind., Mar. 11, 1987), reprinted at App. 29.

The Court of Appeals for the Seventh Circuit affirmed in part and reversed in part. Williams v. Faulkner, 837 F.2d 304 (1988). In its view, the District Court had wrongly equated the standard for failure to state a claim under Rule 12(b)(6) with the standard for frivolousness under § 1915(d). The frivolousness standard, authorizing sua sponte dismissal of an in forma pauperis complaint "only if the petitioner cannot make any rational argument in law or fact which would entitle him or her to relief," is a "more lenient" standard than that of Rule 12(b)(6), the court stated. 837 F.2d, at 307. Unless there is "`indisputably absent any factual or legal basis'" for the wrong asserted in the complaint, the trial court, "[i]n a close case," should permit the claim to proceed at least to the point where responsive pleadings are required. Ibid. (citation omitted).

Evaluated under this frivolousness standard, the Court of Appeals held, Williams' Eighth Amendment claims against two of the defendants had been wrongly dismissed. Although the complaint failed to allege the level of deliberate indifference necessary to survive a motion to dismiss under Rule 12(b)(6), at this stage of the proceedings, the court stated, "we cannot state with certainty that Williams is unable to make any rational argument in law or fact to support his claim for relief" against these defendants. 837 F.2d, at 308. Accordingly, the Court of Appeals reversed and remanded these claims to the District Court. The Court of Appeals affirmed the dismissal of Williams' due process claims as frivolous, however. Because the law is clear that prisoners have no constitutionally protected liberty interest in remaining in a particular wing of a prison, the court stated, Williams could make no rational argument in law or fact that his transfer violated due process. Id., at 308-309.

We granted the petition for a writ of certiorari, 488 U.S. 816 (1988), filed by those defendants against whom Williams' claims still stand to decide whether a complaint that fails to state a claim under Rule 12(b)(6) is necessarily frivolous within the meaning of § 1915(d), a question over which the Courts of Appeals have disagreed. We now affirm.

II

The federal in forma pauperis statute, enacted in 1892 and presently codified as 28 U.S.C. § 1915, is designed to ensure that indigent litigants have meaningful access to the federal courts. Adkins v. E. I. DuPont de Nemours Co., 335 U.S. 331, 342-343 (1948). Toward this end, § 1915(a) allows a litigant to commence a civil or criminal action in federal court in forma pauperis by filing in good faith an affidavit stating, inter alia, that he is unable to pay the costs of the lawsuit. Congress recognized, however, that a litigant whose filing fees and court costs are assumed by the public, unlike a paying litigant, lacks an economic incentive to refrain from filing frivolous, malicious, or repetitive lawsuits. To prevent such abusive or captious litigation, § 1915(d) authorizes federal courts to dismiss a claim filed in forma pauperis "if the allegation of poverty is untrue, or if satisfied that the action is frivolous or malicious." Dismissals on these grounds are often made sua sponte prior to the issuance of process, so as to spare prospective defendants the inconvenience and expense of answering such complaints. See Franklin v. Murphy, 745 F.2d 1221, 1226 (CA9 1984).

The brevity of § 1915(d) and the generality of its terms have left the judiciary with the not inconsiderable tasks of fashioning the procedures by which the statute operates and of giving content to § 1915(d)'s indefinite adjectives. Articulating the proper contours of the § 1915(d) term "frivolous," which neither the statute nor the accompanying congressional reports defines, presents one such task. The Courts of Appeals have, quite correctly in our view, generally adopted as formulae for evaluating frivolousness under § 1915(d) close variants of the definition of legal frivolousness which we articulated in the Sixth Amendment case of Anders v. California, 386 U.S. 738 (1967). There, we stated that an appeal on a matter of law is frivolous where "[none] of the legal points [are] arguable on their merits." Id., at 744. By logical extension, a complaint, containing as it does both factual allegations and legal conclusions, is frivolous where it lacks an arguable basis either in law or in fact. As the Courts of Appeals have recognized, § 1915(d)'s term "frivolous," when applied to a complaint, embraces not only the inarguable legal conclusion, but also the fanciful factual allegation.

Where the appellate courts have diverged, however, is on the question whether a complaint which fails to state a claim under Federal Rule of Civil Procedure 12(b)(6) automatically satisfies this frivolousness standard. The petitioning prison officials urge us to adopt such a per se reading, primarily on the policy ground that such a reading will halt the "flood of frivolous litigation" generated by prisoners that has swept over the federal judiciary. Brief for Petitioners 7. In support of this position, petitioners note the large and growing number of prisoner civil rights complaints, the burden which disposing of meritless complaints imposes on efficient judicial administration, and the need to discourage prisoners from filing frivolous complaints as a means of gaining a "`short sabbatical in the nearest federal courthouse.'" Id., at 6, quoting Cruz v. Beto, 405 U.S. 319, 327 (1972) (REHNQUIST, J., dissenting). Because a complaint which states no claim "must be dismissed pursuant to Rule 12(b)(6) anyway," petitioners assert, "delay[ing] this determination until after service of process and a defendant's response only delays the inevitable." Reply Brief for Petitioners 3.

We recognize the problems in judicial administration caused by the surfeit of meritless in forma pauperis complaints in the federal courts, not the least of which is the possibility that meritorious complaints will receive inadequate attention or be difficult to identify amidst the overwhelming number of meritless complaints. See Turner, When Prisoners Sue: A Study of Prisoner Section 1983 Suits in the Federal Courts, 92 Harv. L. Rev. 610, 611 (1979). Nevertheless, our role in appraising petitioners' reading of § 1915(d) is not to make policy, but to interpret a statute. Taking this approach, it is evident that the failure-to-state-a-claim standard of Rule 12(b)(6) and the frivolousness standard of § 1915(d) were devised to serve distinctive goals, and that while the overlap between these two standards is considerable, it does not follow that a complaint which falls afoul of the former standard will invariably fall afoul of the latter. Appealing though petitioners' proposal may appear as a broadbrush means of pruning meritless complaints from the federal docket, as a matter of statutory construction it is untenable.

Rule 12(b)(6) authorizes a court to dismiss a claim on the basis of a dispositive issue of law. Hishon v. King Spalding, 467 U.S. 69, 73 (1984); Conley v. Gibson, 355 U.S. 41, 45-46 (1957). This procedure, operating on the assumption that the factual allegations in the complaint are true, streamlines litigation by dispensing with needless discovery and factfinding. Nothing in Rule 12(b)(6) confines its sweep to claims of law which are obviously insupportable. On the contrary, if as a matter of law "it is clear that no relief could be granted under any set of facts that could be proved consistent with the allegations," Hishon, supra, at 73, a claim must be dismissed, without regard to whether it is based on an outlandish legal theory or on a close but ultimately unavailing one. What Rule 12(b)(6) does not countenance are dismissals based on a judge's disbelief of a complaint's factual allegations. District court judges looking to dismiss claims on such grounds must look elsewhere for legal support.

Section 1915(d) has a separate function, one which molds rather differently the power to dismiss which it confers. Section 1915(d) is designed largely to discourage the filing of, and waste of judicial and private resources upon, baseless lawsuits that paying litigants generally do not initiate because of the costs of bringing suit and because of the threat of sanctions for bringing vexatious suits under Federal Rule of Civil Procedure 11. To this end, the statute accords judges not only the authority to dismiss a claim based on an indisputably meritless legal theory, but also the unusual power to pierce the veil of the complaint's factual allegations and dismiss those claims whose factual contentions are clearly baseless. Examples of the former class are claims against which it is clear that the defendants are immune from suit, see, e. g., Williams v. Goldsmith, 701 F.2d 603 (CA7 1983), and claims of infringement of a legal interest which clearly does not exist, like respondent Williams' claim that his transfer within the reformatory violated his rights under the Due Process Clause. Examples of the latter class are claims describing fantastic or delusional scenarios, claims with which federal district judges are all too familiar.

To the extent that a complaint filed in forma pauperis which fails to state a claim lacks even an arguable basis in law, Rule 12(b)(6) and § 1915(d) both counsel dismissal. But the considerable common ground between these standards does not mean that the one invariably encompasses the other. When a complaint raises an arguable question of law which the district court ultimately finds is correctly resolved against the plaintiff, dismissal on Rule 12(b)(6) grounds is appropriate, but dismissal on the basis of frivolousness is not. This conclusion follows naturally from § 1915(d)'s role of replicating the function of screening out inarguable claims which is played in the realm of paid cases by financial considerations. The cost of bringing suit and the fear of financial sanctions doubtless deter most inarguable paid claims, but such deterrence presumably screens out far less frequently those arguably meritorious legal theories whose ultimate failure is not apparent at the outset.

Close questions of federal law, including claims filed pursuant to 42 U.S.C. § 1983, have on a number of occasions arisen on motions to dismiss for failure to state a claim, and have been substantial enough to warrant this Court's granting review, under its certiorari jurisdiction, to resolve them. See, e. g., Estelle v. Gamble, 429 U.S. 97 (1976); McDonald v. Santa Fe Trail Transportation Co., 427 U.S. 273 (1976); Bivens v. Six Unknown Fed. Narcotics Agents, 403 U.S. 388 (1971); Jones v. Alfred Mayer Co., 392 U.S. 409 (1968). It can hardly be said that the substantial legal claims raised in these cases were so defective that they should never have been brought at the outset. To term these claims frivolous is to distort measurably the meaning of frivolousness both in common and legal parlance. Indeed, we recently reviewed the dismissal under Rule 12(b)(6) of a complaint based on 42 U.S.C. § 1983 and found by a 9-to-0 vote that it had, in fact, stated a cognizable claim — a powerful illustration that a finding of a failure to state a claim does not invariably mean that the claim is without arguable merit. See Brower v. County of Inyo, 489 U.S. 593 (1989). That frivolousness in the § 1915(d) context refers to a more limited set of claims than does Rule 12(b)(6) accords, moreover, with the understanding articulated in other areas of law that not all unsuccessful claims are frivolous. See, e. g., Penson v. Ohio, 488 U.S. 75 (1988) (criminal defendant has right to appellate counsel even if his claims are ultimately unavailing so long as they are not frivolous); Christiansburg Garment Co. v. EEOC, 434 U.S. 412, 422 (1978) (attorney's fees may not be assessed against a plaintiff who fails to state a claim under 42 U.S.C. § 1988 or under Title VII of the Civil Rights Act of 1964 unless his complaint is frivolous); Hagans v. Lavine, 415 U.S. 528, 536-537 (1974) (complaint that fails to state a claim may not be dismissed for want of subject-matter jurisdiction unless it is frivolous).

Our conclusion today is consonant with Congress' overarching goal in enacting the in forma pauperis statute: "to assure equality of consideration for all litigants." Coppedge v. United States, 369 U.S. 438, 447 (1962); see also H.R. Rep. No. 1079, 52d Cong., 1st Sess., 1 (1892). Under Rule 12(b)(6), a plaintiff with an arguable claim is ordinarily accorded notice of a pending motion to dismiss for failure to state a claim and an opportunity to amend the complaint before the motion is ruled upon. These procedures alert him to the legal theory underlying the defendant's challenge, and enable him meaningfully to respond by opposing the motion to dismiss on legal grounds or by clarifying his factual allegations so as to conform with the requirements of a valid legal cause of action. This adversarial process also crystallizes the pertinent issues and facilitates appellate review of a trial court dismissal by creating a more complete record of the case. Brandon v. District of Columbia Board of Parole, 236 U.S.App.D.C. 155, 158, 734 F.2d 56, 59 (1984), cert. denied, 469 U.S. 1127 (1985). By contrast, the sua sponte dismissals permitted by, and frequently employed under, § 1915(d), necessary though they may sometimes be to shield defendants from vexatious lawsuits, involve no such procedural protections.

To conflate the standards of frivolousness and failure to state a claim, as petitioners urge, would thus deny indigent plaintiffs the practical protections against unwarranted dismissal generally accorded paying plaintiffs under the Federal Rules. A complaint like that filed by Williams under the Eighth Amendment, whose only defect was its failure to state a claim, will in all likelihood be dismissed sua sponte, whereas an identical complaint filed by a paying plaintiff will in all likelihood receive the considerable benefits of the adversary proceedings contemplated by the Federal Rules. Given Congress' goal of putting indigent plaintiffs on a similar footing with paying plaintiffs, petitioners' interpretation cannot reasonably be sustained. According opportunities for responsive pleadings to indigent litigants commensurate to the opportunities accorded similarly situated paying plaintiffs is all the more important because indigent plaintiffs so often proceed pro se and therefore may be less capable of formulating legally competent initial pleadings. See Haines v. Kerner, 404 U.S. 519, 520 (1972).

We therefore hold that a complaint filed in forma pauperis is not automatically frivolous within the meaning of § 1915(d) because it fails to state a claim. The judgment of the Court of Appeals is accordingly

Affirmed.