The antibacterial actions of soy sauce, sawa-wasabi, ginger and garlic on the viability of Vibrio parahaemolyticus were examined mainly at 5°C. Sawa-wasabi acted most strongly and rapidly of these spices, only in soy sauce, and not alone. Allylisothiocyanate, the main pungent component of sawa-wasabi had the same action as sawa-wasabi. Ginger had a strong inhibitory action by itself, but showed no synergy with soy sauce. Garlic did not exert its action even in soy sauce. The antibacterial mechanism of soy sauce is suggested to be due at least to the co-operation of its pH (4.5-4.7), Aw (below 0.9) and the content of sodium chloride (10-18%).