Ultraviolet (UV) irradiation from the sun has been epidemiologically and mechanistically linked to skin cancer, a spectrum of diseases of rising incidence in many human populations. Both non-melanoma and melanoma skin cancers are associated with sunlight exposure. In this review, we discuss the UV wavelength-dependent formation of the major UV-induced DNA damage products, their repair and mutagenicity and their potential involvement in sunlight-associated skin cancers. We emphasize the major role played by the cyclobutane pyrimidine dimers (CPDs) in skin cancer mutations relative to that of (6–4) photoproducts and oxidative DNA damage. Collectively, the data implicate the CPD as the DNA lesion most strongly involved in human cancers induced by sunlight.