Ultraviolet radiation is estimated to be one of the most important risk factors for nonmelanoma and melanoma skin cancers. Athletes practicing outdoor sports receive considerable UV doses because of training and competition schedules with high sun exposure, and in alpine sports, by altitude-related increase of UV radiation and reflection from snow- and ice-covered surfaces. Extreme UV exposure in outdoor sports such as skiing, mountaineering, cycling, or triathlon has been documented in a series of dosimetric studies. Sweating because of physical exercise may contribute to UV-related skin damage as it increases the individual photosensitivity of the skin, facilitating the risk of sunburns. Large epidemiological studies showed that recreational activities such as sun exposure on the beach or during water sports were associated with an increased risk of basal cell carcinoma, whereas skiing has been shown to be at increased risk for squamous cell carcinoma. Risk factors of cutaneous melanoma such as the number of melanocytic nevi and solar lentigines have been found to be more frequent in subjects practicing endurance outdoor sports. An increased risk for cutaneous melanoma may be assumed for these athletes. In addition to the important sun exposure, exercise-induced immunosuppression may increase the risk for nonmelanoma skin cancer and cutaneous melanoma in athletes. Frequently, athletes seem to know little about the risk of sun exposure. Protective means such as avoiding training and competition with considerable sun exposure, choosing adequate clothing, and applying water-resistant sunscreen still need to be propagated in the community of outdoor sportsmen.