Desert bighorn sheep (Ovis canadensis) have been extirpated from much of their historical range in the Chihuahuan Desert. Understanding their dietary preferences in the Chihuahuan Desert is integral to their successful restoration. We evaluated differences (sexual, temporal, and spatial) in the diets of desert bighorn sheep from Elephant Mountain Wildlife Management Area in the Chihuahuan Desert of western Texas by using microhistological analysis of 432 fecal pellet groups (209 rams, 209 ewes, 14 lambs) collected every 2 weeks between September 1998 and August 2000. Ninety-four plant species were identified; bighorn sheep diets consisted of 50% browse, 35% forbs, 11% grasses, and 4% succulents. Diets of rams and ewes did not differ annually. Diets differed seasonally (P < 0.05); forbs prevailed in diets of rams during winter. Diets of bighorn sheep from Elephant Mountain were compared to previously determined diets from the Beach, Baylor, and Sierra Diablo mountains. There were significant differences among female diets between Elephant Mountain and Beach Mountain during winter and the Sierra Diablo Mountains in fall, winter, and summer. Dietary overlap was greatest among desert bighorn sheep at Elephant Mountain and the Sierra Diablo Mountain populations (57.6%), followed by Baylor Mountain (55.7%) and Beach Mountain (52.0%). Dietary overlap among all ranges was highest in the browse component (53%), followed by forbs (23%), grasses (16%), and succulents (8%).