The effect of selenium on the lethal action of ultraviolet radiations and on the lipid peroxidation induced by exposures to ultraviolet A (320-400 nm; 360 kJ.m-2) and ultraviolet B (290-320 nm; 2 kJ.m-2) have been measured in cultured human skin fibroblasts. The experiments have been performed with either pure selenium or a spring water containing selenium and other trace elements (zinc and strontium). For cells cultured in a standard medium containing 10% fetal calf serum, no effect of selenium or spring water addition to the culture medium was observed on the lethality or on the peroxidative process induced by ultraviolet A and B radiations. Concurrently, there was no detectable increase of the seleno-dependent glutathione peroxidase activity. For cells previously depleted in selenium by a culture in a medium containing only 2% serum, a protective effect of selenium can be detected. Depending on the fibroblast donor, we observed (1) a protective effect on lethality of dividing fibroblasts induced by ultraviolet A radiations, (2) a protective effect on lipid peroxidation induced by ultraviolet A radiations on dividing or quiescent fibroblasts and (3) an increase in glutathione peroxidase activity in fibroblasts.