High-pressure entrained-flow gasifier technology is used to convert solid carbonaceous feedstocks into synthesis gas, which can be used in an integrated gasification combined cycle power plant or as a feedstock for chemical or synthetic fuel production. Computational fluid dynamics (CFD) models, once validated, can be used to help design full-scale reactors. Model validation entails the comparison of model predictions to lab-scale or pilot-scale measurements. However, experimental measurements of high-pressure pilot-scale gasifiers usually consist only of wall temperatures and outlet gas temperature and composition, which are of limited use for model validation when the gasifier is operating well, providing information only about operating temperature, heat loss, and equilibrium gas composition. These do not provide a strong validation of the CFD model, whose main purpose is to make predictions of the flame size and shape and its ability to convert solid fuel to gas efficiently in a small volume. This paper presents a model validation based on data generated using CanmetENERGY's 1 MWth high-pressure entrained-flow gasifier. To provide a stronger validation, the approach taken here is to compare the model predictions to the pilot-scale measurements over a range of operating conditions comprising higher (approximately 90%) carbon conversion and lower (approximately 80% or lower) carbon conversion. In effect, the comparison includes operating conditions for which gasification reactions are extended or delayed toward the outlet in order to capture key effects. It is found that the present CFD model is able to track the performance of the gasifier over the range of operating conditions and provides insight into the causes for limited carbon conversion.