UV radiation can induce definitive ultrastructural and biochemical alterations in the dermis of the human skin that are independent of the aging process. We present observations on the solubility of collagen and the ratio of type III/type I collagen in skin protected from the sun (abdomen/axilla) and exposed to the sun (neck/face) in 15 subjects, together with histological and immunohistochemical data on the same subjects. The solubility of collagen in acetic acid was similar for protected and exposed skin and solubility in the pepsin-digestable fraction was not significantly altered by chronic sun damage. This indicates that UV radiation does not affect synthesis or cross-link formation of the collagen chains of the human skin in vivo. Further studies indicated that the proportion of type III collagen in pepsin-soluble fraction was not increased in actinic damage. These findings were in line with immunohistochemical studies using antibodies to type III procollagen.