The leaves of sage (Salvia officinalis L., Lamiaceae) contain high amounts of phenolic diterpenes such as carnosol and carnosic acid. These compounds display antioxidant and anti-inflammatory effects in vitro. Here, we have investigated the anti-inflammatory potency of a sage extract (SE) rich in phenolic diterpenes in vivo using the ultraviolet (UV) erythema test. In a prospective randomised double-blind placebo-controlled study, test areas on the backs of 40 healthy volunteers were irradiated with the 1.5-fold minimal erythema dose. Subsequently, the test areas were treated occlusively with 2% SE in a hydrophilic ointment, compared to 1% hydrocortisone and 0.1% betamethasone as positive controls, and the vehicle alone as placebo. Erythema values were measured photometrically prior to irradiation and after 48 hours. Compared to placebo, SE significantly reduced the ultraviolet-induced erythema, to a similar extent as hydrocortisone. These data suggest that SE might be useful in the topical treatment of inflammatory skin diseases.