Chemical properties and the behavior on gel filtration of proteins in pressed cake from soy sauce mash were investigated for the purpose of utilizing the pressed cake. The pressed cake contained more than 25% of proteins, and the amino acid score was 62, which was almost equal to that of wheat protein. Lysine was the first limiting amino acid in the pressed cake proteins, which were rich in aromatic amino acids. Most of the protein were extracted by aqueous solutions containing urea, SDS or sodium hydroxied, respectively. The isoelectric point of the protein was suggested to be about 3.5 on the basis of solubility behavior. Broad bands and an immobile band were detected in gel electrophoresis, but any sharp band was not detected. The immobile proteins were suggested to be come from wheat gluten, and only 5 kinds of hydrophobic amino acids were detected as their N-terminal amino acids. 25% of the extracted proteins and 52% of their fraction prectipitated by TCA were soluble in methanol. Polymerized proteins corresponding to V₀ (void volume) peak on Sepharose CL-6 B column were prominently observed after 41 days of fermentation, and the proteins which were detected on gel filtration of the fraction extracted with 0.25 M NaOH from the pressed cake, were suggested to be the core of the plymerized protein.