This paper presents a zone model of liquid pool fires burning in an open environment. The model is a system of coupled non-linear equations which contains physical parameters for which reliable values are not currently available. With a judicious estimate of these parameters, the model was tested on various size fires burning three types of fuel. The predicted results are comparable with experimental results from three groups of earlier workers. Sensitivity analyses were run to determine the relative influence of each estimated parameter on the predicted results. These analyses show that efficiency of combustion in the fire is the most important estimated parameter in this model.