Randy P. Rumsey appeals from the district court’s 1 dismissal, for lack of juris *790 diction, of his petition for review of an agency determination that his claim for disability insurance benefits was barred by administrative res judicata. We affirm. A federal district court’s jurisdiction to review decisions regarding disability benefits is governed by 42 U.S.C. § 405(g). That section provides for review only of a “final decision of the Commissioner ... made after a hearing.” An agency’s application of res judicata 2 or refusal to reopen a prior determination is not a “final decision” within the meaning of section 405(g). King v. Chater, 90 F.3d 323, 325 (8th Cir. 1996). But there is a narrow exception where the Commissioner reconsiders the merits of an application previously denied. Id. (citing Jelinek v. Heckler, 764 F.2d 507, 508 (8th Cir. 1985)). Such a claim is treated as having been reopened as a matter of administrative discretion and is, therefore, subject to judicial review to the extent it has been reopened. Id.

The Commissioner dismissed Rumsey’s current application for disability insurance benefits as duplicative of an earlier, unsuccessful claim that alleged the same disability. After a hearing, an Administrative Law Judge (“ALJ”) dismissed Rumsey’s present claim as barred by the final decision in his earlier claim. The ALJ did not consider the merits of the earlier claim, but, as the district court noted, merely “made a threshold inquiry into the facts and evidence of the previous application to determine if the regulatory requirements for reopening the previous claim had been met.” Because the ALJ did not reopen Rumsey’s earlier claim, and because its dismissal for res judicata was not a “final decision” within the purview of 42 U.S.C. § 405(g), we have no jurisdiction to review it. We affirm the judgment of the district court.