Power consumption and mass transfer volumetric coefficient were measured with several sizes of mixing vessels and ring spargers. When the ratio of sparger radius to impeller radius was more than 1.3, the decrease of aerated mixing power consumption was suppressed, and the optimal position of the sparger was found. The action of aerated mixing power was correlated with the ratio of sparger clearance to impeller clearance. In addition, the power consumption and mass transfer volumetric coefficient in large-scale vessels (3m(3) and 4m(3)) were measured, and it was shown that the mass transfer volumetric coefficient can be correlated with the equation of Sato et al. (1989).