The clinical efficacy of a combination of medetomidine, butorphanol and midazolam for anaesthesia in dogs, and its reversal by atipamezole, was evaluated in two experimental groups of four adult beagle dogs and compared with a control group of four dogs receiving only midazolam and butorphanol. The anaesthetic procedure was used for surgical procedures in another group of 14 dogs. After the injection of medetomidine, a rapid loss of coordination followed by mild sedation was observed. Anaesthesia was attained 2 +/- 1 minutes after the administration of butorphanol and midazolam and lasted 82 +/- 5 minutes, the dogs recovered 51 +/- 6 minutes later and there were no side effects. Analgesia and skeletal muscle relaxation were optimal throughout the period of anaesthesia. Statistically significant bradycardia and hypothermia were observed but there were no significant effects on respiratory function. After atipamezole the dogs recovered their normal posture, heart rate and body temperature in less than 20 minutes. In the control group, the short-lived light sedation was accompanied by inadequate analgesia and poor muscle relaxation. In the surgical group, no differences, except in drug requirements, were recorded in comparison with the experimental groups. Good analgesia and muscle relaxation, total absence of side effects and stability in vital body functions were observed. The injection of atipamezole was always effective, devoid of side effects and induced recovery in less than 20 minutes.