A computer program designed to model the turbulent reacting flow in jet-stirred reactors has been developed. In solving the single-phase flow field, a two-equation turbulence closure was used to predict the turbulent eddy viscosity variation in the reactor. The model was used to predict the performance of a real reactor. The predicted results compared favorably with measurements in the field. It was found that the key to the reactor performance is the strength of the recirculating eddy caused by the jet entrainment.