To study the cumulative influence of UV irradiations on skin matrix alterations, human skin fibroblasts were irradiated successively three-fold, at 24h intervals, with UVA (3×5J/cm2), UVB (3×8mJ/cm2), UVA plus UVB (3×5J/cm2and 3×8mJ/cm2) and the levels of 92kDa gelatinase (pro-MMP9), 72kDa gelatinase (pro-MMP2) and plasma-membrane elastase type protease were determined, following subsequent 24-h culture in 10% serum-containing medium. UV irradiations had only minor influence (1.4-fold increase for UVB) on secreted levels of pro-MMP2and decreased the amount of plasma membrane elastase produced by cells. It did however, for UVA and UVB alone, induce a significant increase of 66kDa activated MMP2production: 2.5- and 1.7-fold respectively. Such enhancement was not observed when combined irradiations were administered. UV exposure possessed a much higher influence on pro-MMP9secretion by dermal fibroblast enhancing enzyme levels by 2.5-, 6.5- and 5-fold for UVA, UVB and UVA+UVB, respectively.