A patient with painless, bluish-red skin lesions under immunosuppressive treatment for kidney transplantation is presented. The clinical and histological diagnosis was Kaposi's sarcoma. This is a rare but serious complication in the immunocompromised patient. Human Herpes virus 8 (HHV 8) was recently found in the lesions from patients with Kaposi's sarcoma. This supports the important role of immunosuppression in the development of this tumor. Therapy consists of reduction or stopping of the immunosuppressive drugs which is usually followed by reduction in tumor mass. Local skin tumors can be treated with irradiation or laser therapy. In the case of lesions of visceral organs chemotherapeutic regimens consisting of vinicristine/bleomycin are indicated. New strategies aim to reduce the virus load with antiviral drugs or to inhibit the angiogenesis of this highly vascularized tumor.