Antagonistic effects of atipamezole(50, 100, 200, 400 $mu extrm{g}$/kg, i.m.) on sedation induced with xylazine (2 mg/kg, i.m.) were evaluated in dogs. Atipamezole at doses of 100~400$mu extrm{g}$/kg effectively reversed sedation, and the arousal time, standing time and total recovery time were significantly shortened. The optimal action of atipamezole was seen at a dose of 100 $mu extrm{g}$/kg. At this dose recovery from sedation was quick and smooth, and adverse effects such as hyperactivity or tachycardia were minimal with or without atropine premedication.