Blood flow was measured by the 133Xe technique in normal and corticosteroid-treated skin. Epicutaneous and intracutaneous methods of tracer application were compared in normal skin. The two labeling methods were equally suitable for measuring cutaneous blood flow provided calculations in both cases were based on a biexponential resolution of the wash-out curve in its cutaneous and subcutaneous components and provided the traumatic hyperemia phase was considered, when intracutaneous application of the tracer was used. Results were invalidated if calculations were based on initial slope of the wash-out curves.Topical application of beta-methasone valerate in a reduction in cutaneous blood flow as measured by the intracutaneous technique with curve resolution, whereas no effect could be demonstrated when calculations were based on the initial slopes of the curves. The 133Xe technique is a simple and reliable method for measuring cutaneous blood flow, which might prove useful in estimations of penetration ability and potency of topical corticosteroids.