Abstract: The cAMP levels in involved and uninvolved skin of 22 Psoriatic patients were determined by protein binding method. Two improvements is skin biopsy techniques were made; (1)including all epidermis and dermis in the sainpies; (2)moving the samples of involved and uninvolved skin at the same time to avoid any artificial changes due to ischemic effect, The result showed. that the cAMP level in inyolved skin was significantly lower than that in uninvolved skin, The authors considered that psoriasis was related to the cAMP deficiency.