To elucidate the relative contribution of the different UV portions of sunlight in solar mutagenesis, we investigated the mutagenic specificities of UVC, UVB, UVA radiation and simulated sunlight (SSL) at an endogenous gene in repair -proficient and -deficient rodent cells. We also examined the DNA damage distribution, including bipyrimidine photoproducts and oxidative damage, in purified DNA and in DNA from rodent cells irradiated with UVC, UVB, UVA and SSL. Such a data base highlights a role for UVA in the production of mutagenic photolesions.