Histidine-rich protein from newborn rat epidermis has been further characterized. Polyacrylamide gel electrophoresis in 8 M urea demonstrated dissociation of the protein, a possible oligomeric series, and one major band with two minor bands of the, pH 5.0 precipitate. Amino acid analysis correlated well with previous analyses (except for lower levels of histidine), while the amino acids of high content increased with purification. Sedimentation coefficients and molecular weights determined by ultracentribfugation of all monomers and the residual tissue in histidine-rich protein were in agreement with estimates from gel filtration chromatography. Lower values were obtained for keratohyalin granule proteins. Isoelectric focusing indicated diisoelectric properties of the protein. A molecular model of deamidation is presented in an attempt to explain this property.