Kaposi's sarcoma (KS) is a recognised complication following kidney transplantation, but the incidence varies according to the geographical area. Although it is a rare tumour, its incidence increases dramatically after solid‐organ transplantation. The immunosuppressive medications reactivate human herpes virus 8, which has been proposed as the offending agent. The usual treatment of KS is to reduce immunosuppression, chemotherapy and radiotherapy. Nevertheless, the mortality still remains considerably high and has been reported between 8 and 14%. Sirolimus (SRL) has properties which may be useful in the management of some post‐transplant tumours such as KS. We report a renal transplant patient with KS, who had multiple relapses after radiotherapy but responded well to the change of immunosuppression from cyclosporine to SRL.