A patient with HIV-related immune thrombocytopenic purpura (HIV-ITP) had a rapid rise in platelet count when treated with interferon-alpha-2b, 3 million units three times weekly. There were no significant toxicities with therapy. His platelet count fell to pretreatment levels when therapy was discontinued, then increased again when therapy was reinstituted at 1.5 million units three times weekly. Interferon-alpha-2b, administered continuously at low doses, is well tolerated, effective, and possibly less immunosuppressive than other treatments for HIV-ITP.