The paper presents the results of mapping fire severity for the FROSTFIRE experiment at different spatial scales. The finest spatial data was collected before the fire on a grid of 160 intensive and 226 dispersed ground plots designed to study fuel bed and vegetation characteristics. Those plots were re-measured after the fire to re-characterize vegetation, determine ground fire severity, and estimate effects on carbon pools and emissions. The second spatial data scale was gathered from aerial stereo photography before and after the fire. The prefire aerial photography (1 inch=500 feet) was used to produce an enhanced map of vegetation types currently existing in the C4 watershed. The map includes 11 vegetation types and smaller patches that allowed us to map the vegetation mosaic across the watershed. Post fire aerial photos were interpreted and digitized to produce a fire severity map that includes 5 classes. The classes are based on the canopy condition observed on the post-fire photos. Those classes were: blackened, scorched, mixed, green lit, and green no lit. The severity map allowed us to investigate the relation of aerial burn severity with pre-fire fuel bed characteristics, vegetation patterns, slope and aspect, fuel moisture, observed fire behavior from infrared imagery, and weather observations during the fire. These FROSTFIRE results will assist fire scientists to better understand the fire process across multiple ecosystems ranging from the boreal forests in Alaska to the tropical forests in Brazil.