Kaposi's sarcoma is a neoplastic vascular lesion. Its form of onset is frequently disseminated, especially in HIV-positive patients. Its association with the infection caused by a virus of the Epstein-Barr family, human herpesvirus 8 (HHV-8), has been recently demonstrated. In this article we discuss the unusual presentation of a solitary manifestation of Kaposi's sarcoma on the penis of a 53-year-old HIV-negative patient. Polymerase chain reaction analysis of the tumor tissue was positive for HHV-8 in the tumor cells but not in the reactive stroma cells surrounding the tumor. The case is interesting for its unusual site of presentation, the young age of onset, the association with HHV-8 infection, the HIV-negative serology, and the benign course of the disease.