A 53-year-old white woman had severe hemolytic anemia while taking nomifensine. A drop of hemoglobin to 61 g per I prompted the transfusion of two units of packed red cells. Nine days later, severe thrombocytopenia with multiple petechiae ensued. Both hemolysis and thrombocytopenia resolved promptly upon withdrawal of the drug and short-term prednisolone treatment. Serologic studies showed nomifensine-dependent, metabolite-specific red cell antibodies as the cause of immune-mediated hemolysis and, in serum samples obtained after purpura, strong platelet-specific PlA1 and weak HLA antibodies suggested a diagnosis of posttransfusion purpura.