Accurate mapping of wildfires is critical to fire management. Technological advances in remotesensing and Geographic Information Systems (GIS) over the last decade have been widely incorporated into wildfire mapping and management, but neither have been assessed for accuracy nor compared to established manual methods. Since Landsat-based mapping of wildfires willsoon replace manual mapping methods, this type of comparison is critical to understanding the strengths of each method. Landsat ETM+ imagery was classified to create fire perimeter maps for 53 fires in Nevada, USA. These maps were then assessed for agreement with published, manually mapped fire perimeters. Published perimeters were found to correlate poorly to remotely sensed fire perimeters, and significantly overestimated area burned (p ? 0.05) by an average of 18 percent. Mapping disagreement was then correlated to a measure of topographic roughness at four spatial scales to determine whether increasing terrain complexity was a factor in increased disagreement. Mapping disagreement showed a significant positive correlation (r = 0.57) to topographic roughness. For fire research spanning multiple decades, these results indicate that it may be difficult to utilize fire perimeter data sets comprising both satellite-derived and manually mapped perimeters because the two data sets are significantly different.