The mass transfer rates of a gaseous reactant into a liquid where the reactions are catalyzed by homogeneous catalysts have been evaluated by the numerical solution of the diffusion-reaction equations according to Higbie's penetration theory. The concentration profiles as well as enhancement factors are discussed as functions of the kinetic rate constants and the diffusion coefficients of the catalytic intermediates. In addition to the complex catalytic model, two simplified models were applied in order to facilitate design calculations. One version was obtained by application of the Bodenstein approximation; the simplest version comprised only the stoichiometric reaction. The Bodenstein model provides a very good approximation except for deviating diffusion coefficients of the catalytic intermediates. The applicability of the stoichiometric model is not as wide as with the Bodenstein model, but for some conditions acceptable approximations are achieved. (c) 2006 American Institute of Chemical Engineers.