The relationship between alkaline adaptation and the resistance against environmental stresses was examined in Vibrio parahaemolyticus. Alkali-adapted cells were found to. have increased resistance against various stresses, including heat, crystal violet, deoxycholic acid, and hydrogen peroxide. However, alkali-adapted cells showed no increased resistance against acid stress and heat-adapted cells did not show increased resistance against alkaline stress. Furthermore, alkaline treatment induced cell elongation with heterogenous size of the bacterium.