A patient with a pure seminoma presented with severe IgG-mediated warm autoimmune hemolytic anemia. Monoclonal IgM-kappa cryoglobulinemia and a biological false positive test for syphilis were also found. Treatment directed at both the seminoma and the hemolysis resulted in the complete disappearance of these antibodies. It is possible that these immunological phenomena occurred in response to the tumor. The occurrence of warm autoimmune hemolytic anemia and monoclonal paraproteinemia in association with solid tumors is reviewed.