Cases of thrombotic thrombocytopenic purpura (TTP) have been reported in patients who are infected with the human immunodeficiency virus (HIV).1,2 Recently, manifestations resembling TTP have been reported in HIV-infected patients who were treated with high-dose valacyclovir hydrochloride, 8 g/d.3 We report here a case of TTP in an HIV-infected patient who was treated with a lower dose of valacyclovir.