In 8 of 1009 patients receiving renal grafts and consecutive immunosuppressive therapy during the last 20 years in Budapest, Hungary, Kaposi's sarcoma developed 6.5 months (average) after transplantation. Of 8 cutaneous cases of this disease, 5 also presented visceral manifestations. Seven patients died. Those with visceral tumors died because of the tumor itself. One patient affected by cutaneous tumor has survived for 5 years post-treatment. The relatively high incidence of Kaposi's sarcoma may be explained by a high infection rate with Herpes virus 8, which was shown to be positive in all three cases investigated.