Across the Western United States, the structure of many low-elevation dry conifer forests is considerably different than it was prior to Euro-American settlement. These altered conditions contribute to the increased probability of unnaturally severe and extensive wildfires. Strategies for reducing fuels and restoring fire-adapted ecosystems include thinning live and dead trees and burning surface fuels to reduce the risk of severe surface and crown fires. In the past decade, hazardous fuels have been reduced on nearly 30,000 square miles by federal and state agencies. These treatments may be effective in initiating short-term changes in forest structure and may shift existing diameter distributions toward those that might persist in late-successional forests, but single treatments or entries are insufficient to mitigate structural changes resulting from nearly a century of fire exclusion. This work was done as part of the National Fire and Fire Surrogates Study.