Sixty-four free-ranging polar bears (Ursus maritimus) were immobilized using carfentanil at doses ranging from 1.0–38.0 μg/kg (mean 20 ± 8 μg/kg). Induction was rapid (5.0 min) (n = 46) and the bears showed good muscle relaxation. Respiratory rate was depressed (mean 3.8 bpm). The mean arousal after the administration of narcotic antagonists was longer than 5 min. Recurrence of narcotic effects—so called recycling—was seen in some bears and in a separate black bear trial was consistently observed in animals given doses of 10 μg/kg or more of carfentanil. The rapid induction, low drug volume and excellent muscle relaxation related to carfentanil immobilization make this a potentially useful drug for polar bear immobilization.