Histopathological changes under occulsive dressing with 0.1% triamcinolone acetonide cream, 0 025% fluocinolone acetonide cream, and 1% hydrocortisone cream were compared each other and with the changes following topical application of 5% ammoniated mercury ointment without occulsion in five cases of psoriasis vulgaris. 1) The earliest changes noticed were the diminution of the papillary edema, the appearence of the granular layer and the disappearence of parakeratosis. 2) A week after treatment, the remarkable changes revealed were the thinning of the epidermis, the diminution of acanthosis, papil]ary edema and cell infiltration of the upper dermis and the appearence of the granular layer. 3)The capillary dilatation remained unchanged even two weeks after treatment in all groups. 4) Among these drugs, the best respanse revealed was triamcinolone cream, the next was fluocinolone cream. The response of hydrocortisone cream was poorer than fluocinolone cream and ammoniated mercury ointment was even more poorer than hydrocortisone cream.