Clobetasol propionate-d5 is intended for use as an internal standard for the quantification of clobetasol propionate by GC- or LC-MS. Clobetasol propionate is a corticosteroid. It binds to glucocorticoid receptors in a cell-free assay and inhibits proliferation of primary human skin fibroblasts when used at a concentration of 5 µg/ml. Topical administration of clobetasol propionate reduces croton oil-induced ear edema in mice. Formulations containing clobetasol propionate have been used in the treatment of inflammatory skin conditions.