HIV-seropositive patients who belong to the three major acquired immunodeficiency syndrome (AIDS) risk groups may develop an idiopathic thrombocytopenic purpura (ITP) which is related to the HIV infection. HIV-associated ITP clinically resembles classic ITP but, in spite of very low platelet numbers, bleeding is rarely severe, and moderate splenomegaly and lymphadenomegalies are seldom present. Treatment is the same as that given for classic ITP because the pathogenesis is in many ways similar. Immunosuppressors can be dangerous in the case of retrovirosis, and splenectomy may lead to AIDS. High doses of immunoglobulins often give an improved platelet count but this tends to be short-lived, and long-term periodical infusions usually lose therapeutical effect. Alpha interferon gives conflicting results and Danatrol is not usually effective. Specific anti-D immunoglobulins produce a high percentage of positive results and may be administered for long-term maintenance without side effects. Zidovudine (AZT) may produce a good platelet increase in a large number of patients, but there is no consensus for the use of this anti-retroviral drug in otherwise asymptomatic HIV-positive patients. In conclusion, since it is very unusual for bleeding to occur, moderate thrombocytopenia is best left untreated because a spontaneous increase in platelet count is possible. But if the platelet count is very low, or if bleeding is present, treatment is mandatory and must produce a rapid platelet increment with minimal side effects.