We report two cases of thrombotic thrombocytopenic purpura (TTP) in advanced stage HIV-positive patients (CD4+ < 0.05 x 10(9)/L). Clinical symptoms were relevant, but their course was not fulminant; the two patients responded to different therapies (plasma or plasma plus plasmapheresis, and steroids), showing rapid improvement in symptoms. One patient remained asymptomatic with zidovudine only, while the other relapsed (probably due to an intercurrent infection). This second person is now asymptomatic on zidovudine plus low doses of steroids.