The vasoconstrictor effect of various topical steroids applied to protected and occluded skin is described. The method indicates that acetates are better absorbed than the parent alcohol, while the phosphate salts are poorly absorbed. In the case of triamcinolone, the formation of the acetonide leads to greatly enhanced percutaneous absorption. The use of a plastic film over these compounds leads to a 100-fold increase in absorption when compared with simple topical application. Using vasoconstriction as an index of absorption, it is suggested that the method may be of use in determining the penetrability and activity of new compounds.