Fire spread through chaparral fuels is a significant feature of wildland fire in southern California. In order to study the detailed physical processes involved during fire spread, FIRETEC, a coupled atmosphere/wildfire behavior model was refined to examine chaparral fire behavior. FIRETEC combines a sophisticated fine-scale model to simulate a three- dimensional wildfire, moving over a terrain-following finite volume grid, with the motions of the local atmosphere. It accounts for the microscopic details of a fire with macroscopic resolution by dividing quantities into mean and fluctuating parts and the resulting transport equations are solved by using a finite difference method. In this paper, fire spread through live chaparral fuels under different burning conditions was studied. Specifically, the effect of varying environmental variables and physical characteristics of fuels on fire spread was examined. Results from four simulations are presented. They demonstrate the effects of wind speed in enhancing heat transfer from the fire to unignited fuel ahead of the fire front. Increased fuel loading and packing ratio resulted in decreased rate of spread; while increased fuel moisture reduced the predicted rate of spread, consisted with our laboratory scale experiments.