Wildfire poses threats to public safety and property in many Wildland-Urban Interface (WUI) areas. We describe a spatial Decision Support System (DSS) that can be used to help evaluate fuel treatment measures for WUI areas in terms of their impact on burn probabilities across the landscape. Our DSS is embedded in a computer-based geographic information system (GIS) platform that describes the structure of the landscape, its fuel mosaic, where structures and other values at risk are located and where fires might ignite and how they might spread across the landscape. It has a graphic interface that includes a digital map of the landscape on which fire managers and planners can delineate areas where proposed fuel treatment activities might take place. Mathematical models of fire ignition, suppression and spread processes are used to predict the potential impact of such measures on the landscape and display those impacts on a burn probability map which shows the predicted probability that any point on the landscape will burn given the current landscape and the proposed fuel treatment measures that are to be evaluated.