In this report, incidence and clinical characteristics of Kaposi's sarcoma (KS) were retrospectively analyzed among renal transplant recipients who were being followed-up in the outpatient clinic of the Istanbul School of Medicine. Between October 1983 and December 1997, 17 cases of KS were diagnosed among 557 patients (3%). Of the total 25 post-transplant malignancies, KS was the most common tumor, representing a rate of 68%. Diagnosis was suspected with typical skin lesions and was confirmed by biopsy. Gastroduodenal endoscopy was applied to 7 patients in order to assess gastrointestinal tract involvement. Of the total number of patients diagnosed with KS 14 were male and 3 female, with the mean age of 40 +/- 15 (range 13-68) yr. The mean duration between the date of transplantation and diagnosis of KS was 15.9 +/- 20.3 (range 1-65) months. The lesions were limited to the skin in 13 patients, while skin and gastrointestinal tract were involved in 2 patients and generalized disease was noted in 2 patients. The initial therapeutic approach was to withdraw cyclosporine and to reduce azathioprine. In the case of progression of the lesions azathioprine was also stopped. Besides, surgical excision of the lesions, radiotherapy and/or chemotherapy were performed according to the clinical picture. Remission was observed in 14 patients after this therapy protocol. The 2 patients with gastrointestinal involvement and 1 patient with generalized KS died in spite of the above-mentioned therapeutic interventions. One of the patients on remission died of pneumonia. It was concluded that KS carried a high risk of morbidity and mortality in renal transplant recipients, and tapering of immunosuppression, especially withdrawal of cyclosporine, affected the prognosis favorably.