We monitored changes in vegetation and channel morphology along reaches of two perennial streams, Limestone Canyon and East Cedar Creek, on the White Mountain Apache Reservation in Arizona starting in the fall of 1995. Enormous wildfires caused extensive erosion and runoff in the watersheds containing the sites in 2002 and 2003, respectively. All reaches within the Limestone Canyon site suffered severe channel downcutting, lateral erosion, and removal of herbaceous and shrubby vegetation from the streamsides. At East Cedar Creek, the channel aggraded without noticeable bank erosion, and most of the herbaceous vegetation remained intact. Many differences between the two sites likely account for the different responses to post-wildfire floods. Most of the watershed of Limestone Canyon burned severely, while only a much smaller portion of the East Cedar Creek watershed was burned. Limestone Canyon is located in a moderately steep valley with canyon walls composed of coarse limestone and sandstone materials, while East Cedar Creek is located in a flatter, broader valley where silty substrates predominate. Prior to the fire, the geology and geomorphology of the East Cedar Creek site had facilitated luxuriant growth of soil-binding graminoids that protected the stream bed from scour. Due to the large differences between the sites, it is difficult to determine which factors were most important in shaping their response to wildfire. However, because most of the differences are highly correlated across the landscape, it is possible to predict which areas are most likely to be damaged by wildfire. The steep canyons of the Mogollon Rim appear particularly vulnerable to lasting impacts from wildfire.