In this retrospective study, rituximab was found to be effective therapy in 10 of 11 patients with splenic marginal zone lymphoma, inducing prompt reduction in splenomegaly, improvement in blood counts in 9 patients and clearance of a pleural effusion in 1 patient. Median response duration was 21 months (range 4 to 37 months). Two patients who relapsed at 21 and 23 months responded to retreatment. Rituximab should be considered in patients who are poor candidates for splenectomy.