In resuscitating dogs subjected to ten minutes of circulatory arrest due to ventricular fibrillation, a number of drugs were used with artificial ventilation of the lungs, external cardiac massage, and external electrical counter-shock. Resuscitation was more successful when epinephrine was used than when no drug therapy or sodium bicarbonate were used. Combination of lidocaine with epinephrine increased the frequency of defibrillation, but circulation was not restored more often than with epinephrine alone. The use of methoxamine hydrochloride was followed by successful resuscitation more often than was the use of epinephrine. Combination of epinephrine and sodium bicarbonate was as effective as methoxamine in restoring circulation, and inspection of the survivors after 24 hours suggested that the combination might be preferable.