We present a case of human herpes virus 8 (HHV8)-associated Kaposi sarcoma (KS) occurring in a renal allograft ureter from a male donor. The female patient presented with a rising creatinine due to ureteric obstruction, and subsequent histological examination of the excised tumor revealed a KS. The tumor tested positive for HHV8 antigen and, using in situ hybridization to identify X and Y chromosomes, we were able to demonstrate that the tumor was of male origin. In the absence of any other KS lesions, this suggested that the tumor arose due to reactivation of latent HHV8 in the donor tissue, permitted by the recipient's immunosuppression. The patient was managed by a gradual reduction in immunosuppression and there has been no subsequent recurrence of the tumor. KS in renal transplantation is discussed in detail including the possible utility of pre-transplant HHV8 screening.