A computer code for the parallel simulation of a utility boiler is evaluated and its parallel performance is investigated. The comparison of the predicted incident heat¯uxes on the walls with experimental data has revealed a satisfactory agreement. The parallel calculations were performed on a Cray T3D using up to 128 processors.If radiative transfer is not considered and a ®xed number of iterations is prescribed, a speedup of 95 is achieved using 128 processors. In this case the pressure correction task is the least ecient one. If the calculations proceed up to convergence, the radiation becomes the least ecient task. This is not a major issue if the number of processors is small, but for 128 processors the radiation is already the most timeconsuming task and strongly in¯uences the overall eciency.