We initiated a prospective multicenter phase II trial using rituximab and temozolomide in immunocompetent patients with progressive or recurrent primary central nervous system lymphoma (PCNSL) based on activity observed in retrospective studies. Treatment consisted of an induction phase with rituximab (750 mg/m(2)) on days 1, 8, 15 and 22 and temozolomide (150 mg/m(2)) days 1-7 and 15-21, followed by six cycles of consolidation temozolomide (150-200 mg/m(2) × 5/28 days), followed by maintenance with methylprednisolone (1 g IV every 28 days) until progression. Sixteen patients were enrolled, and a complete response was seen in 2/14 (14%) evaluable patients. The median progression-free survival was 7 weeks and median overall survival was not reached (median follow-up: 37 months). Treatment was well tolerated, but due to slow accrual and preliminary analysis suggesting futility, the trial was closed early. Given the overall modest activity, this regimen should be reserved for patients who are not candidates for other, more aggressive salvage treatments.