The project is concerned with modeling the long-term effects of landscape fuel treatment patterns on wildfire sizes and severity. The work was initiated based on theoretical fuel treatment patterns that appeared effective at changing fire growth across large landscapes, thus reducing the acreage burned and the chances that large fires starting far from urban interface areas will reach them. To model long-term effect, vegetation/fuel dynamics are simulated using a custom version of FVS PPE (parallel processing extension), a fire growth simulation model similar to FARSITE, and a spatial fuel treatment optimization program developed for this project. Simulations are run into the future for 50 years to examine the effects of implementing spatially optimized fuel treatment patterns on fire sizes, burn probabilities, and fire growth rates. These response variables are compared for random arrangements of treatments as well. Effects of spatial constraints on placement of fuel treatments (e.g. stream corridors, private lands, wildlife restrictions on treatments) on treatment performance are also studied. Study sites are located in western Montana, the Sierra Nevada of California, and eastern Oregon.