A series of laboratory fire experiments were conducted in fuel beds consisting of either excelsior (wood wool), or 6.35 mm sticks, or a mixture of these. Tests were done both with and without wind. Various characteristics of the fire, including rate of spread and fireline intensity, were compared with predictions from the Rothermel model. The behavior of the mixed fuel fires, compared to that of the fires in the constituent fuels, did not agree well with the predictions of the model. We conclude that, in order to model the behavior of fire in mixed fuels, the Rothermel model needs modification.