Background: The higher frequency of malignant skin tumors is of great significance in renal transplant recipients (RTRs) who should receive immunosuppressive therapy for a long time. This study was designed to determine the frequency of malignant skin tumors in RTRs in Imam Reza Hospital, Mashhad, Iran, in 2001-2002.Method: This descriptive study was performed on 322 recipients who were examined by a dermatologist for malignant skin tumors in the renal transplant unit. A questionnaire containing a detailed history of age, sex, and site of the lesion, time of transplantation, occupation, and time of cancer development was completed for patients with a biopsy proven skin cancer.Result: Nine patients (2.8%) had malignant skin tumors. Five patients (55.55%) had Kaposi sarcoma (KS) and 4 patients (44.44%) had non melanoma skin cancer (NMSC). The mean age of the patients was 44.4 ±11.4 years. Eight patients (88.88%) were male. The mean time to development of Kaposi sarcoma and NMSC development was 9.1 months and 5.75 years, respectively. Three patients (60%) with Kaposi sarcoma had lesions on lower extremities and all the NMSCs were located in the head and neck region. Outdoor occupations were seen in at least 50% of NMSCs.Conclusion: This study again showed the importance of regular dermatologic examination for early diagnosis of skin malignancies, particularly, in high risk groups including renal transplant recipients.