Current fire models have focussed on spread in dead, small-diameter fuels. Fires in predominantly living vegetation account for a large proportion of annual burned area nationally. Prescribed burning is used to manage living fuels; however, prescribed burning is currently conducted under conditions that result in marginal burning. We do not quantitatively understand the relative importance of the fuel and environmental variables that determine spread in live vegetation. A laboratory study to determine the effects of wind, slope, moisture content, and fuel characterstics on fire propagation in several common chaparral fuels will be described. Preliminary results indicate that the presence of wind is very important to propagation success in these moist fuels. An equation to predict fire spread success will be developed using logistic regression and the laboratory data.