Abstract: Methods for topical treatment of psoriasis are disclosed comprising applying to the skin a composition comprising an effective amount of a therapeutically active and physiologically acceptable prostaglandin A.sub.2, prostaglandin J, derivative of prostaglandin A.sub.2, derivative of prostaglandin J, an alkyl ester of prostaglandin A having 1-10 carbons in the alkyl group, or a benzyl ester of prostaglandin A, in a vehicle for topical application. Methods for inhibiting an increased proliferation of cell growth associated with psoriasis in epidermis are further disclosed comprising topically applying to the epidermis an effective amount of a therapeutically active and physiologically acceptable prostaglandin A, prostaglandin J, derivative of prostaglandin A or derivative of prostaglandin J, in a vehicle for topical application.