The combination of medetomidine, azaperone, and alfaxalone has been successfully used to anesthetize captive white-tailed deer (Odocoileus virginianus). This same combination was utilized to immobilize free-ranging female mule deer (Odocoileus hemionus; MD) in urban and nonurban environments (14 urban MD, 14 nonurban MD) in British Columbia, Canada. Physiologic data were collected to assess the safety and reliability of this drug combination under field conditions. Each deer received estimated dosages of 0.15 mg/kg medetomidine, 0.2 mg/kg azaperone, and 0.5 mg/kg alfaxalone intramuscularly via a remote darting system. Inductions were calm and rapid (mean time to sternal recumbency: urban MD, 6.4±2.2 min; nonurban MD, 8.2±4.1 min). Supplemental drugs were required to induce lateral recumbency in five deer, four of which had experienced initial dart failure (mean time to lateral recumbency: urban MD, 8.5±3.8 min; nonurban MD, 18.7±16.5 min). Recoveries were smooth and uneventful (time to standing: urban MD, 12.5±3.4 min; nonurban MD, 9.0±3.5 min) for all but one debilitated nonurban MD that died shortly after atipamezole administration (at five times the medetomidine dose). The major side effects of the combination were hypoxemia and hypercapnia. The combination of medetomidine, azaperone, and alfaxalone proved suitable for the immobilization of urban and nonurban free-ranging MD.