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During May-July, 1981-85, 111 black bears (Ursus americanus) were immobilized with ketamine (x̄ = 5.0 mg/kg) and xylazine (x̄ = 2.0 mg/kg). Time from complete immobilization to recovery (walking) ranged from 22 to 140 min. We experimented with yohimbine (0.04-0.35 mg/kg) to counteract immobilization and thereby speed recovery. Eleven bears were given intramuscular injections of yohimbine, of which only 2 (18%) recovered within 10 min. In contrast, 35 bears were given intravenous injections of yohimbine, of which 31 (89%) recovered within 10 min (median = 5 min). Heart rates increased an average of 61% within 1 min of intravenous injections. Two bears that were immobilized with ketamine alone (10 mg/kg and 17 mg/kg) did not recover within 10 min after intravenous injection of yohimbine, although their heart rates increased appreciably. These data suggest that yohimbine antagonizes the effects of xylazine but likely does not counteract the effects of ketamine. We tested 3 dosages of yohimbine with respect to the dosage of xylazine (0.05, 0.10, and 0.15 mg yohimbine/mg xylazine) and found no differences in recovery times. Also, no relationships were observed between recovery times after yohimbine injection and the weight, age, or sex of the bear, dose of yohimbine given, time since immobilization (range 10-66 min), or the dose of ketamine given (range 2.7-8.9 mg/kg). We conclude that an intravenous injection of 0.05 mg yohimbine/mg xylazine provides a safe and effective antagonist to ketamine-xylazine immobilization in black bears.