BACKGROUND: Skin cancer following solid organ transplantation is an important cause of morbidity in long-term survivors. This risk is well known but imprecisely quantified. OBJECTIVES: We aimed to determine: (i) the skin cancer risks in transplant patients more precisely; (ii) whether the risk of malignant melanoma is altered; and (iii) whether the risk of epithelial cancers occurring at non-exposed sites is comparable with that seen in sun-exposed sites. METHODS: We linked a population-based cohort of 5356 patients who had received organ transplants in Sweden between 1970 and 1994 with the compulsory Swedish Cancer Registry, to identify all cancer cases except basal cell carcinomas, which are not registered. RESULTS: After a mean follow-up of 5.6 years post-transplantation, 172 of 5356 patients developed 325 non-melanoma skin cancers (excluding basal cell carcinomas) and six malignant melanomas. The relative risk of non-melanoma skin cancer was 108.6 [95% confidence interval (CI) 94.6-123.1] for men and 92.8 (95% CI 73.2-116.0) for women. The highest risks were noted for upper limbs, and the risk increased with time. No significant increase in malignant melanomas was noted: the relative risk was 1.6 (95% CI 0.5-3.7) for men and 0.5 (95% CI 0. 0-2.6) for women. Except for the lip, which is also sun-exposed, other epithelial sites did not show comparable increases in cancer risk. CONCLUSIONS: We conclude that organ transplant recipients are at a highly increased risk for non-melanoma skin cancer and must be closely followed throughout their lives. Cancer risk associated with transplantation is higher for sun-exposed than for non-sun-exposed epithelial tissues, even among populations living in regions with low solar insolation.