C lobetasol propionate, probably the most potent topical corticosteroid yet developed,' has recently been approved for use in the United States. Confirming vasoconstrictor assay predictions of clinical effectiveness,^ clobetasol has been shown in doubleblind, multicenter trials^'* to be statistically significantly superior in 0.05% cream formulation to 0.05% fluocinonide cream and in 0.05% ointment formulation to 0.05% betamethasone dipropionate in an optimized vehicle in the treatment of psoriasis. Clobetasol propionate cream 0.05% has also been compared with the potent topical corticosteroid cream haleinonide 0.1% in a recent two-center study. The results of the 2-week randomized double-blind, left-right paired trial (the most accurate comparative measure of topical corticosteroid efficacy in psoriasis) are presented below. Materials and Methods Clobetasol and haleinonide creams were applied twice daily for 2 weeks, in quantities not exceeding 50 g per week, by 73 patients with moderate-to-severe psoriasis. (Identical blind-labeled tubes of cream were randomly marked for use on patients' right or left sides.