P>Background Organ transplant recipients (OTRs) have an increased risk of developing skin cancer, especially epithelial tumours. A number of factors such as immunosuppression, age, ultraviolet radiation and skin type are considered as important in aetiology. Objectives The purpose of this study was to further evaluate the risk factors for OTRs regarding skin cancer after transplantation. A detailed investigation of the specific compounds of sun exposure was realised. Methods A questionnaire-based study was performed in a specialist OTR dermatology clinic from January to April 2009. The subjects were 70 organ transplanted patients who had developed some form of skin cancer after transplantation. As controls served 69 organ transplanted patients who had no history of skin cancer. The controls were matched concerning age, transplanted organ and gender. Photo protection, sun exposure and transplantation data were part of the questionnaire. Statistical analysis was performed with Mann-Whitney-U-test, chi-square test or Fisher's exact test. Results The total sun burden (TSB) and the recreational sun exposure in particular attained higher scores in the skin cancer group (TSB-score: mean 11 center dot 8 vs. 10 center dot 0, P < 0 center dot 05; recreational sun exposure: mean 6 center dot 3 vs. 5 center dot 1, P < 0 center dot 05). The skin cancer group had fairer skin types than the control group (median skin type 2 vs. 3, P < 0 center dot 05). The OTRs who developed skin cancer have been more likely to have a history or present intake of azathioprine (mean 42% vs. 21%, P < 0 center dot 05). Also, the skin cancer group has been transplanted for a longer time (mean 12 center dot 3 vs. 7 center dot 2 years, P < 0 center dot 001), analogously had a younger age at transplantation (mean 49 center dot 5 vs. 52 center dot 7 years, P < 0 center dot 001). Conclusions Recreational sun exposure is of central importance for OTRs. A long period of transplantation and thus immunosuppression presents a main risk factor for the development of skin cancer in OTRs. A multi disciplinary management with the best medication and a focus on sun protection is needed to prevent skin cancer in OTRs.