Sympatry can create special dynamics between populations and impact management strategies for each species. We estimated size and overlap of home ranges and core areas of sympatric female mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus) in west-central Texas. We captured 50 mule deer and 53 white-tailed deer, fitted them with radiocollars, and monitored them during 2000-2002. Average (±SE) size of home range of mule deer in spring was 3.9 ± 0.32 km2, while that of white-tailed deer was 4.32 ± 0.77 km2; sizes of home ranges in summer were 2.82 ± 0.32 and 2.08 ± 0.23 km2, respectively. Interspecific overlap of home range between seasons was similar to intraspecific overlap. Overlap in core area also was similar within and between species during summer, but interspecific overlap in core area was less during spring.