Petitioner appeals from a judgment dismissing his petition for post-conviction relief. At the time that he filed the petition, petitioner already was litigating a post-conviction case involving the same underlying convictions. The post-conviction court dismissed the petition under ORCP 21 A(3) on the ground “that there is another action pending between the same parties for the same cause” and, alternatively, on the ground that ORS 138.550(3)1 barred the petition. On appeal, petitioner does not dispute that his pending post-conviction proceeding was “another action pending between the same parties for the same cause” for purposes of ORCP 21 A(3). He nonetheless contends that ORCP 21 A(3) does not apply to post-conviction proceedings and, thus, that the post-conviction court erred when it dismissed the petition under that provision. He argues further that the dismissal cannot be sustained under ORS 138.550(3) because, in his view, the post-conviction court applied the wrong legal standard when determining whether to dismiss the petition under that provision.

We affirm. Petitioner did not dispute the applicability of ORCP 21 A(3) below and, consequently, his unpre-served contention that the trial court erred by applying that provision in the context of a post-conviction proceeding does not provide grounds for reversal.2 Beyond that, petitioner— properly—does not dispute that there was, in fact, “another *881action pending between the same parties for the same cause.” ORCP 21 A(3). Petitioner’s pending post-conviction proceeding was exactly that. The post-conviction court therefore correctly dismissed the petition under ORCP 21 A(3), and we need not address the correctness of the court’s determination that ORS 138.550(3) also required dismissal.3 We reject any additional contentions in petitioner’s pro se supplemental brief without written discussion.

Affirmed.