Thrombotic thrombocytopenic purpura (TTP) is a rare but well-described complication of HIV infection, which occurs equally frequently during the early asymptomatic phase of HIV infection and with clinical AIDS. The clinical spectrum varies from a low-grade asymptomatic thrombocytopenia with mild renal insufficiency to a catastrophic illness with gross neurological deficits and renal failure requiring dialysis. We report two cases of TTP associated with HIV infection seen in our institution over a period of 2 years. The clinical course of these two patients highlights the markedly heterogeneous characteristics of patients with HIV-related TTP. HIV infection may be the most common association of TTP in certain communities with a high prevalence of HIV infection. As early diagnosis and institution of plasmapheresis is crucial for a favorable outcome it is important to be aware of this association.