The case of a renal transplant recipient with a known history of iv drug abuse but unknown human immunodeficiency virus (HIV) status who presents after having a stable renal allograft function for 4 yr, with acute/subacute advanced renal failure, nephrotic syndrome, and hypertension, as well as clinical and histologic findings of thrombotic microangiopathy, is reported. He was subsequently found to have a positive serology for HIV-1 with a low CD4 count but no clinical manifestations of the acquired immunodeficiency syndrome. He was treated conservatively with zidovudine (AZT). The patient never regained graft function and was ultimately discharged from the hospital on maintenance dialytic therapy. This is, to our knowledge, the first report of thrombotic microangiopathy in an HIV-1-infected patient presenting late in the course as acute/subacute renal allograft failure.