To the editor: Kaposi's sarcoma is a rare manifestation of the acquired immunodeficiency syndrome (AIDS) in hemophiliacs (1). We describe a case with a rapidly progressive clinical course and other unusual aspects. A 30-year-old heterosexual man with severe hemophilia A had a high-potency alloantibody to factor VIII. Between referral to us (1975) and June 1985, he was treated with an average of 9000 IU/year of factor VIII concentrates (manufactured in the United States) and 9500 IU/year of factor IX concentrates (only heated concentrates were used since 1984). At visits in 1983 and 1984, the patient, who denied using illicit drugs