We evaluated a treatment strategy targeting both lymphoma cells (by rituximab) and the microenvironment (by thalidomide) in 16 patients with relapsed/refractory mantle cell lymphoma (MCL). Rituximab was administered at 375 mg/m(2) for 4 weekly doses concomitantly with thalidomide (200 mg daily, with a dose increment to 400 mg on day 15), which was continued as maintenance therapy until progression/relapse. Thirteen patients (81%) experienced an objective response, with 5 complete responders (31%). Median progression-free survival (PFS) was 20.4 months (95% confidence interval [CI], 17.3-23.6 months), and estimated 3-year survival was 75%. In patients achieving a complete response, PFS after rituximab plus thalidomide was longer than PFS after the preceding chemotherapy. Severe adverse events included 2 thromboembolic events and 1 grade IV neutropenia associated with thalidomide. Our results suggest that rituximab plus thalidomide has marked antitumor activity in relapsed/refractory MCL and a low toxicity profile, which warrants further evaluation in MCL.