A mathematical model for predicting the course of a developing fire in a compartment is described. The model uses release rate data obtained from laboratory-scale tests to calculate the rate of heat and smoke generation within the compartment. From these data, the model predicts rate of involvement of combustible surfaces, upper layer temperatures, and smoke concentration as a function of time. The model is described by relationships used to determine: (i) ignition and rate of vertical fire propagation, (ii) release rates based on total heat released and incident flux, and (ii) heat losses by venting and accumulation within the boundaries of the compartment. Results of predicted by the model and observed in full-scale tests of furnished compartments are compared.