Based on the finding that the bubbling-controlling condition, the agitation-controlling condition, or the intermediate condition may predominate in an aerated mixing vessel, correlative equations for kLa valid for a wide range of operating conditions are proposed. In addition, the type of mixing of the gas phase in aerated mixing vessels is discussed, and plug-flow type mixing is recommended since the logarithmic mean value of entrance and outlet compositions of gas gives a reasonable gas absorption rate.