Many highly exothermic gas-liquid reactions are carried out with a vaporizing solvent, which after condensation is returned to the reactor. In this way the liberated reaction heat for a large part is absorbed by the cooling water flowing through the condenser. In order to determine the influence of this evaporation on the behaviour of an agitated gas-liquid tank reactor a model second order reaction was studied. The temperature dependence of the enhancement factor is strongly affected by the solvent evaporation. The influence of several design and operation parameters such as liquid residen time, dilution of reactant with solvent, air excess in the gas phase and reactor pressure on the conversion and the reactor pressure is demonstrated. Multiplicity for the chosen model reaction will only occur under rather severe conditions. The theory developed is applied to an industrial air oxidati of a hydrocarbon.