An imperfectly stirred reactor (ISR) is a model that can be applied to strongly recirculating reactive flows. This model, which is based on the conditional moment closure method, uses the simplifying approximation that conditionally averaged reactive scalars are independent of position in the reactor. This approximation results in simple ordinary differential equations in mixture fraction space. The simplicity of the model permits use of quite complex chemical kinetics with a relatively small computational cost. In this work the ISR model is applied to an experimental combustor. The first step in themodeling is to obtain the mixture fraction PDFs at positions inside the reactor. To do this, flow and mixing fields are calculated using a computational fluid dynamics code based on a k -epsilon model and fast chemistry method. Results are then used as input to the ISR code. Mean values of the reactive scalars are compared with experimental data obtained from measurements performed on a burner at the University of Sydney. The comparison shows good agreement in the case of CO, CO2 , and temperature, but the methodology still needs to be improved.