Temperature-sensitive, radiotelemetry transmitters were used to measure body temperatures of six free-ranging, adult, female mule deer (Odocoileus hemionus) in the semi-arid shrub-steppe of southcentral Washington from 1988 to 1990. Body temperatures ranged from 37.5 to 39.7°C and were similar to rectal temperatures reported for Odocoileus. Temperatures followed distinct circannual and circadian patterns unrelated to changes in air temperature or solar radiation. Behavioral thermoregulation may have been important in helping deer avoid thermal stress at environmental temperatures that often exceeded 25°C. On hot, clear days, deer sought beds that provided refuge from solar radiation yet permitted radiative heat loss.