Homogenated stratum coreum, callus and psoriatic scales were extracted with (1) phenol water (PW) and (2) the combined use of trypsin digestion and phenol water extraction (TPW). The serological properties of the various preparations obtained were compared, using indirect haemagglutination, absorption and inhibition tests. The PW and TPW water phases contained two different antigens which were common to all three tissues. In addition, the periodate-treated TPW water phase of stratum corneum contained an erythrocyte-sensitizing antigenic determinant. This, however, cross-reacted with the untreated and periodate-treated preparation of psoriatic scales, whereas callus lacked the determinant present after treatment with periodate. Apparently callus and psoriatic scales lacked some components present in stratum corneum, but determinants specific for callus or psoriatic scales were not detected.