Aging of the skin progresses chronologically under the influence of sunlight exposure. Degradation and remodeling of the extracellular matrix proteins by proteinases is generally thought to be a crucial event during the process of photoaging. In this study, we examined the immunoreactivity of matrix metalloproteinase 1 (interstitial collagenase; MMP-1) and elastase in sun-exposed and un-exposed female skin. Frozen sections were reacted with monoclonal antibodies against human MMP-1 and elastase, and then visualized with the ABC method. Immunoreactivity of both antigens was observed mainly in the infiltrated mononuclear cells, and was found to be more prominent in the sections from sun-exposed facial skin. A retrospective study with 120 formalin-fixed sections revealed that a decreased amount of collagen and an increased amount of degenerated elastin (elastotic material) were approximately proportional to the age and the infiltrated cell numbers in the sun-exposed facial skin. These results suggest that degeneration of the matrix proteins and elevated expressions of the proteinases are important events during the process of photoaging.