It has become common practice to add sunscreening agents of variable potency to cosmetics to protect against the adverse effects of ultraviolet (UV) radiation exposure. The purpose of this study was to determine whether cosmetic preparations containing sunscreening agents protected against the adverse effects of acute UV radiation exposure and, if so, to identify the components responsible for the photoprotective effects. Pretreatment of skinwith one such cosmetic product provided complete protection against UV-induced erythema, sunburn cell formation and Langerhans cell damage in volunteers, skin types II and III, whose skin was exposed to a 1.5 minimal erythema dose daily for 4 consecutive days. When individual components of the cosmetic preparation were analyzed for their photoprotective activities, it was found that both the cinnamate and benzophenone sunscreen combination and an extract of baker's yeast present in the preparation had photoprotective properties. These studies indicate that incorporation of photoprotective agents into cosmetic preparations provides a beneficial function and should therefore be encouraged.