In the biological treatment of waste gases, the contaminants are first transferred from the gas to the water phase and, subsequently, converted by the microorganisms. If the compound to be removed is poorly water-soluble, the biological degradation is often limited by the slow transport from the gas to the aqueous phase. This transport Limitation can be reduced by dispersing an apolar water-immiscible organic solvent with a high affinity for the pollutants in the aqueous medium. A mathematical model was derived to be able to predict theoretically for which gaseous compounds and at which conditions a relevant intensification of the gas/water transfer can be expected. A characteristic composite gas/water mass transfer coefficient was obtained which is a function of the amount of solvent in the system and of the affinity of the compound for the water and for the solvent. Validation of the model predictions was done by carrying out steady-state experiments in a stirred-tank reactor in the absence of biological degradation. Two compounds were tested namely toluene and oxygen, being moderately and poorly water-soluble, respectively. An increase of the mass transfer coefficient with increasing solvent volume fractions was found. While for oxygen a 2.2-fold increase was found at 15% (v/v) FC40, an enhancement of circa 1.15 was observed for toluene at the same solvent volume fraction. The experimentally determined values of the enhancement factor defined as the ratio between the mass transfer coefficient in the systems with and without solvent compared well with the theoretical model predictions.