The authors describe a 21-year-old man with long-lasting Evans syndrome refractory to corticosteroids and immunosuppressive agents; the patient responded to four weekly infusions of rituximab. The patient relapsed with thrombocytopenia 7 months post-therapy and was successfully re-treated with two weekly doses of the same monoclonal antibody. He remains in remission for 7-plus months after the second treatment. Therapy was well tolerated, and no infectious complications occurred, despite avoiding administration of prophylactic gammaglobulin. Rituximab appears safe and modestly effective in a variety of immune-mediated hematologic diseases, including autoimmune hemolytic anemia, chronic immune thrombocytopenia, Evans syndrome, pure red cell aplasia, mixed type II cryoglobulinemia, cold agglutinin disease, and Waldenströ m's macroglobulinemia. However, as most of the published literature consists of case reports and small case series, international collaboration is essential in order to better define the efficacy and safety of this agent in children and adults with hematologic diseases. Am.