UV irradiation induces lipid peroxidation (LPO) and cell damage. The aim of the present work was the study of UVB radiation effects on cultured human skin fibroblasts, concerning LPO, prostaglandine E2 (PGE2) formation and cell viability. The cells were exposed to 50, 100, and 150 mJ/cm2 of UVB irradiation. Cellular TBARS and supernatant fluorescent substances were measured spectrofluorimetrically. PGE2 was measured using an immunoenzymatic method. Cell viability was evaluated by the MTT test. All determinations were done after a 2 h incubation period post-irradiation. TBARS were increased for all doses of irradiation (p < 0.001). Fluorescent substances differed from controls at 50 mJ/cm2 (p < 0.001). UVB at 100 and 150 mJ/cm2 decreased cellular viability (p < 0.001). An increase of PGE2 was observed with UVB at 150 mJ/cm2 (p < 0.001). These results confirm the occurrence of LPO and cytotoxicity after UV irradiation; on the other hand, this study showed the formation of PGE2 induced by UV light on cultured human skin fibroblasts. We propose a relationship between these phenomena.