The mortality rate of nonmelanoma skin cancer is higher than generally considered. An actual nonmelanoma skin cancer is a risk factor not only for other skin cancers but also for cancers in other organs. The recurrence rate can, according to the method of calculation, yield surprisingly diverging results. Statistical mapping of subclinical tumor growth in basal cell carcinoma supplies the margins for tumor-free excision. An even better but more expensive tool for therapy planning is tumor imaging with magnetic resonance imaging. Psoralen plus ultraviolet light of the A wavelength-treated patients run a dose-dependent risk of developing squamous cell carcinoma of the skin but also cancers in other organs. Human papilloma virus-16 seems not to be associated with squamous cell carcinoma of the skin except for the anogenital region and possibly the finger. The finding of retroviruslike particles in endemic non-acquired immunodeficiency syndrome Kaposi's sarcoma strongly suggests that a virus other than human immunodeficiency virus may play a role in the pathogenesis of this disease.