The rate of hydroformylation of 1-octene catalyzed by a water soluble catalyst is measured in mechanically agitated batch reactor at various stirrer speeds and organic phase holdups. The data have been analyzed by coupling reaction kinetics to a pseudo-homogeneous gas-liquid-liquid model based on Higbie＇s penetration theory which takes into account the presence of the dispersed organic phase. A rapid liquid-liquid mass transfer of the reactants is assumed leading to an equilibrium between the continuous and the dispersed phases. The predicted values of the rate are in good agreement with the experimental one. The depletion of the organic substrate in the continuous phase is found negligible.