In this review the epidemiology and pathogenetic aspects of UV-induced malignant skin tumours (basal cell carcinoma, squamous cell carcinoma and melanoma) are discussed with regard to current literature. Whereas present knowledge, in particular, gained from experimental data, permits substantial conclusions about the development of squamous cell carcinoma, the situation for basal cell carcinoma and melanoma does not appear to be unequivocally clear. One reason for this can be explained by the fact that there exist no adequate animal models for these tumours that could exactly reflect the biological behaviour in man. Although there is no doubt about a causal role of sun exposure, this relationship is based on mere epidemiological facts.