Various treatments for HIV-related thrombocytopenia have been reported. Since etiologies of the thrombocytopenia may differ with regard to risk group treatment outcomes may also vary. We have recently studied the long-term use of zidovudine in individuals with sexually transmitted HIV infection and severe thrombocytopenia. Twenty-five men, median age 34 years (range, 23–51 years), were treated with zidovudine (1000 mg/day) for a median duration of 12 months (range, 2.5-> 26 months). Nineteen patients (76%) had had episodes of symptomatic bleeding secondary to thrombocytopenia prior to study entry. All patients bleeding symptoms resolved with therapy. Six (24%) achieved a complete response, with normalization of platelet counts, while 11 patients (44%) achieved a partial response, giving an overall response rate of 68%. The median time to partial or complete normalization of platelet counts was 12 weeks (range, 4–62 weeks). Toxicities were minimal during the study period. Only one patient developed an AIDS-defining diagnosis while on therapy. We conclude that patients with sexually transmitted HIV infection and immune thrombocytopenia may need a prolonged period of therapy with zidovudine to achieve a platelet response. Other treatment modalities may be required for the 30% of patients who do not respond to zidovudine.