Kaposi's sarcoma (KS) developed among 11 of 416 renal allograft recipients transplanted between 1985 and 2000. Only 3 among 364 Caucasian recipients developed KS, while it affected 8 of 52 Black patients, all of whom had been born in African countries (P <.001). All patients had their immunosuppression reduced; two also received daunorubicin and one received electrotherapy. Three patients developed accelerated renal allograft dysfunction, probably due to the reduced immunosuppression. Remission of KS was observed in seven patients, while lesions stabilized or improved partially in the other four. After resuming dialysis 2 of 11 patients died; both were in KS remission. Human herpes virus-8 (HHV-8) serology and DNA analysis was evaluated in sera obtained from seven donors: all were negative. Conversely, among eight sera collected pretransplant from the nine living recipients, HHV-8 IgG was detected in six and DNA was present in one. HHV-8 IgG was expressed in all patients (9/9) at some point posttransplant; DNA was detected in three patients. Therefore, the robust ethnic predisposition to KS was associated with a high pretransplant prevalence of HHV-8 among African recipients. Although some seroconversions were detected posttransplant, there was no evidence for donor-to-recipient transmission.