The effects of surfactants and antifoam agent on the gas holdup s, the liquid-phase mass transfer coefficient kL and the volumetric liquid-phase mass transfer coefficient kLa in a bubble column were studied experimentally. An addition of surfactants such as //-alcohols to water increases s and decreases kL, and an addition of antifoam agent to water decreases e, kL and kLa. However, the degree of reduction of kL value by an addition of surfactant to water is lower for bubble swarms in a bubble column than that for a single bubble in stagnant liquid. Based on these observations, the previous model for estimating kL of a single bubble in aqueous solutions of surface-active substance is modified so as to be applicable to the estimation of kL for bubble swarms in a bubble column.