The specific and total acid phosphatase activities of all fractions of a differential centrifugation of homogenized normal stratum corneum and psoriatic scales were compared. The main enzyme activities of both tissues were localized in the 105,000 g supernatants, i.e. the cytoplasmatic fractions. The kinetic properties of the cytoplasmatic acid phosphatase of both tissues were studied and the influence of several inhibitors investigated. The enzymes in both tissues could be inhibited by p-chloromercuribenzoate, F––, tartrate, Be2+, Cu2+, and Zn2+. Pb2+ only affected the psoriatic enz