In 126 adult renal transplant recipients who had survived their transplantation for at least 8 years, we determined whether numbers of nevi and the presence of clinically atypical nevi were related to chronic sun exposure. On the basis of a skin examination, three groups were defined: patients with at least one clinically a typical nevus; patients with only clinically normal nevi: and patients without any nevi. The prevalence odds ratio of having any clinically atypical nevi as compared to having only clinically normal nevi was calculated in a logistic model, in relation to gender, skin type, age, sun exposure, and number of keratotic skin lesions present. Similarly, the prevalence odds ratio of having 30 or more nevi compared to fewer than 30 nevi was calculated. We found an inverse association between chronic sun exposure and age with numbers of nevi in adult renal transplant recipients. The presence of clinically atypical nevi was also inversely associated with chronic sun exposure, but this association disappeared after adjustment for age. We did not observe an association of nevi with the number of keratotic skin lesions, nor with humoral immune responses against human papillomavirus and the presence of certain HLA antigens, which are factors associated with nonmelanoma skin cancer in renal transplant recipients. Chronic sun exposure and age appeared to be strong determinants for decreased numbers of nevi in adult renal transplant recipients. Infection with human papillomaviruses does not appear to play an important role.