The effects of fire on the higher elevation Madrean ponderosa pine and mixed conifer ecosystems are examined. Morphological and physiological adaptations of ponderosa, Arizona, Apache, and Chihuahua pines are reviewed and related to the degree of fire tolerance by each species. Similar evaluations are made for mixed conifer species, including Douglas and white fir, Engelmann and blue spruce, southwestern white pine, and aspen. Restoration of fire to these ecosystems is difficult today because of the altered stand conditions resulting from decades of fire suppression. However, by understanding species' fire tolerances and ecological relationships, the manager will be able to implement efficient and effective burning prog rams to improve ecosystem health.