The ecosystems of the Sierra Madres area of Mexico are changing dramatically because of lack of fire. The objective of this study is to characterize the fire regimes of the Sierra Madre Occidental; to investigate the historical and current role of fire in the forest ecosystems; and to study the natural fuel accumulation in non-harvested stands between fire cycles. Preliminary results indicate a decrease in fire frequency since historical times and an increase in fuel lading and density of trees due to fire suppression. This is very similar to what can be found in the Blue Mountains of northeastern Oregon.