This paper reports a comparison of measurements and predictions of wall heat flux, temperature, andgas composition in a full-scale oil-fired utility boiler of 250 MWe. The numerical simulation of complex reactive flows in practical combustion systems is a very demanding problem as far as computational requirements are concerned. To decrease such requirements, a domain decomposition method is employed here. The domain is split into several subdomains, and an independent grid is employed in each one of them to solve the governing equations, visiting sequentially all the subdomains in an iterative fashion. Evaluation of mathematical models requires detailed and accurate experimental data. This question is also addressed in this paper, and measurements of mean temperatures, major gas species concentrations, and wall incident heat fluxes within the radiation chamber are reported here. From the analysis carried out, it is concluded that, on the whole, the predictions are in good agreement with the measurements. Because of the assumption of chemical equilibrium, the CO concentration is overestimated, and the CO 2 concentration is, consequently, underpredicted. Further measurements and predictions at partial load (100 MWe) demonstrate the predictive capability of the model.