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The relatively recent invasion of annual grasses, particularly red brome (Bromus rubens), and growing urbanization into parts of the Upper Sonoran Desert, have contributed to increased fire frequency and intensity which could result in significant long-term changes in the vegetation. Cacti species are an important component of this ecosystem and are particularly susceptible to fire. Not only are cacti easily killed by fire, but most species are slow growing and may require decades or centuries to reestablish their former dominance. A prescribed fire was conducted on the Tonto National Forest, approximately 48 km northeast of Phoenix, to evaluate the response of several environmental variables, including perennial vegetation. The site was burned in June 1985 and monitored intensively for one year. Perennial vegetation was subsequently resampled in June 1996. The two most dominant perennial plants on the study site are a shrub, bursage (Ambrosia deltoidea), and a cactus, buckhorn cholla (Opuntia acanthocarpa). Bursage cover and density declined significantly immediately following fire. Bursage is an aggressive reseeder and while cover remained below preburn levels through 1986, total density increased rapidly following fire due to seedling establishment. By 1996 bursage cover and density (both control and burned sites) were similar to preburn conditions. Buckhorn cholla does not respond well to fire. Cover and density of buckhorn cholla have decreased following the fire and remained below control levels through 1996. The results of this project indicate that fire can significantly alter the plant species composition of this community type. The cacti species may be particularly susceptible. Special fire management techniques may be required to protect this cactus-rich desert plant community that so many people associate with the Phoenix area and the State of Arizona.