Outbreaks of Kaposi's sarcoma, opportunistic infections, and autoimmune thrombocytopenia among homosexual men have recently been described. We report here a case with the combination of Kaposi's sarcoma and autoimmune thrombocytopenia. Our patient presented with Kaposi's sarcoma limited to the integument and autoimmune thrombocytopenia diagnosed by elevated platelet bound IgG. Characteristics of immunosuppression included lymphocytopenia and a reversed blood helper:suppressor T lymphocyte ratio. Immunohistochemical evaluation of skin biopsy specimens revealed tumor cells to contain Factor VIII-related antigen (a vascular endothelial cell marker). In addition some tumor cells stained positively with a monoclonal antibody directed against a cytomegalovirus antigen.