A computer simulation of the buming of large woody natural fuels has been created. The model simulates flaming combustion of large woody surface fuels but includes the influence of smoldering duff on this burning. This paper describes calibration of empirical constants in the model using data from laboratory crib bums and from prescribed bums in harvest debris and in natural fuel accumulations. The calibrated model reproduced laboratory crib burning rates and natural fuel loading reductions with acceptable accuracy.