Seven years of above normal precipitation between 1976 and 1983 encouraged heavy growth of native annuals and exotic grasses in the western Sonoran Desert. Unprecedented fires in creosote bush scrub started mostly after 1978. Analysis of several burns near Palm Springs revealed that most shrubs, including Larrrea tridentata, Ambrosia dumosa and Opuntia spp., are poorly adapted to relatively low intensity fires as evidenced by limited sprouting and reproduction. These shrubs were replaced by open stands of Encelia farinosa, native ephemerals, and European exotics, mostly Bromus rubens and Schismus barbatus. The rapid selective thinning of creosote bush scrub species suggests that the modern biogeography of this ecosystem may be controlled, in part, by recurrent burning.