The annual costs attributable to large fire suppression in three Forest Service Regions (1970-1981) were estimated as a function of fire perimeters using linear regression. Costs calculated on a per chain of perimeter basis were highest for the Pacific Northwest Region, next highest for the Northern Region, and lowest for the Intermountain Region. Recent costs in real terms for the Intermountain and Pacific Northwest Regions are lower when adjusted for fire sizes, indicating that cost calculations based on pre-1976 data may overestimate current costs.