AbstractA novel, acidic histidine‐rich protein, has been extracted from the epidermis of 3‐day‐old rats. This protein was purified through preparative isoelectric focusing, followed by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS‐PAGE). The purified protein had a molecular weight of 56,000 daltons and an isoelectric point of 5.1. The amino acid composition included 17% glycine, 11% glutamic acid, 10% alanine, 4% histidine and 3% tyrosine.Using the immunofluorescent technique, observation showed that the antibody formed as a result of purified antigen was located in the cell membrane of the stratum corneum of the skin.This acidic, histidine‐rich protein could coat the stratum corneum cell membrane and perhaps act as one important component of the epiderma