Nonmelanoma skin cancers are the most common malignant neoplasms of fair-skinned people, in many sunny countries exceeding the total of all other neoplasms. The evidence that the primary causal agent is chronic repeated exposure to solar ultraviolet radiation is overwhelming. The incidence of basal cell carcinoma is always greater than that of squamous cell carcinoma, varying by latitude from 10:1 to 2.5:1. The incidence of nonmelanoma skin cancer has been increasing by 2% to 3% per year, at least in the United States. Most likely, this is caused by greater outdoor exposure for leisure and social reasons.