Knowledge of a species' home range size is useful for numerous areas of study, including body-mass scaling, metabolic requirements, and conservation. Notably lacking are home range size estimates from desert habitats for 2 common mammals, Sylvilagus audubonii and Lepus californicus. I estimated daytime, nighttime, and 24-h home range sizes using telemetry in the Chihuahuan Desert of south central New Mexico. For both species, estimates were larger in nighttime than in daytime, and estimates for S. audubonii were larger for males than for females. I found no evidence for home range “cores.”