The bioactivity of a novel topical glucocorticosteroid, mometasone furoate 0.1 % fatty cream was compared with betamethasone dipropionate 0.05% cream and betametasone valerate 0.1% cream. An ultraviolet light (UV-B)-induced inflammation assay in humans was used, and the combined effect of a single, open application of the corticosteroids was evaluated. Reduction of UV-B induced inflammation was monitored by laser Doppler blood flowmetry, clinical skin scoring and skin reflectance spectrophotometry. Skin scoring and reflectance spectrophotometry were found unsuitable because one of the cream vehicles contained titanium dioxide which shielded skin erythema. Laser Doppler blood flowmetry showed that mometasone furoate 0.1 % fatty cream was more than twofold better in reducing UV-B-induced inflammation than betamethasone dipropionate 0.05% cream and betametasone valerate 0.1 % cream, and that the effect was sustained for at least 24 h after a single application.