The Gates of the Mountains Wilderness and Additions, Montana, have little promise for the occurrence of metallic mineral or fossil fuel resources. This conclusion is based on detailed investigation of the geology and mineral and fossil fuel resources. Geologic structures of the area, although similar to potential petroleum-bearing structures in other parts of the Rocky Mountains overthrust belt, are open to the surface and probably could not have trapped or held hydrocarbons. Rocks that potentially could have generated petroleum have higher levels of thermal maturity than the range of oil generation but are within the range of dry natural gas generation.