We report 17 cases of the classic type of Kaposi's sarcoma in Xinjiang, which is located in the north-western area of China surrounded by Mongolia in the east, Russia in the north and Kazakhstan in the west. Fifteen of the patients were of the Uygur people. All patients were male and did not have acquired immunodeficiency syndrome. Most of the lesions were found in the lower and/or upper extremities, with 16 patients showing multiple lesions. Immunohistochemical examination of the lesions revealed that human herpesvirus 8 (HHV-8)-encoded latency-associated nuclear antigen was expressed in the nuclei of spindle-shaped tumor cells. HHV-8 DNA was detected by polymerase chain reaction in all seven cases examined. Phylogenetic tree analysis revealed that DNA sequences of the HHV-8-encoded K1 gene in the seven Kaposi's sarcoma cases were classified as subtype C that was common in the Mediterranean, the Middle East and East Asian countries. In addition, using immunofluorescence we investigated the seroprevalence of HHV-8 in 73 Uygur patients with diseases other than Kaposi's sarcoma. Surprisingly, the serological study revealed that 34 of the patients (46.6%) were positive for antibodies against HHV-8, suggesting that HHV-8 infection is widespread in Xinjiang area. The occurrence of the classic type of Kaposi's sarcoma with a high seropositivity rate implies that Xinjiang is the most endemic area for HHV-8 infection in the world known to date. Considering that Xinjiang is located at the middle point of the Silk Road that used to extend from Rome to China, these data imply that the virus may have been in circulation in this area due to the migration of the people via the Silk Road.