Several recent studies have demonstrated Kaposi's sarcoma-associated herpes virus (KSHV), also known as putative human herpes virus-8 (HHV-8), DNA in various epidemiologic forms of Kaposi's sarcoma (KS), including AIDS-associated, classic, and endemic types. Risk of developing KS in non-HIV-infected immunosuppressed hosts, such as patients following solid organ transplantation, is also significantly higher compared to normal individuals. We have retrospectively evaluated 28 organ transplant patients with KS (23 cutaneous and five visceral) for the presence of KSHV genome by polymerase chain reaction (PCR) amplification of DNA isolated from formalin-fixed, paraffin-embedded archival tissue samples. 27/28 KS patients were positive for the presence of KSHV. In four KS patients, tissue samples with no histologic evidence of KS were also analysed for KSHV. No evidence of positivity in three samples was noted, but one patient had weak positive amplification products on DNA samples isolated from a gastric biopsy with chronic gastritis and lymph node with sinus histiocytosis. These data support the association of KSHV with KS developing in non-HIV-infected immunosuppressed patients, similar to other forms of KS, and suggest that KSHV may play a significant role in the development of all forms of KS.