Three cases of thrombotic thrombocytopenic purpura (TTP) and coexistent human immunodeficiency virus (HIV) infection are presented with a review of 15 cases reported in the literature. Of the 18 total patients, one-half presented with no symptoms of HIV infection while nine patients presented with symptomatic HIV disease before or simultaneous to the diagnosis. The presenting symptoms were similar to those with classic TTP and included fever in 75% and 40% with neurologic symptoms. Laboratory parameters reflected the microangiopathic hemolytic anemia typically seen in patients with TTP. The median hematocrit was 19.4%, while the median platelet count was 16,000/mm3. As with classic TTP, patients with HIV-related TTP only had mild renal dysfunction (median creatinine of 1.2 mg/dl, range 0.8-4.8 mg/dl). Plasma exchange produced clinical remission in a majority of the patients. Importantly, approximately one-third of the patients died prior to the initiation of therapy. We conclude that TTP is a rare but treatable condition in patients with HIV infection. A TTP diagnosis should be considered in patients with HIV infection who present with severe anemia and thrombocytopenia. Plasma exchange should be considered as initial therapy. The role of both antiplatelet therapy and aspirin is unknown.