A study was done to determine if 12 dogs could be resuscitated from 30 min of ventricular fibrillation if aortic diastolic blood pressure was maintained above 30 mm Hg by administration of epinephrine and, in 6 cases, saline solution during cardiopulmonary resuscitation (CPR). Of the 12 dogs seven were resuscitated successfully. The survivors received 3.4 ± 1.7 mg of epinephrine, whereas the nonsurvivors received 11.1 ± 2.1 mg of epinephrine. The aortic diastolic blood pressure was significantly higher (p < .05) in the survivors at 12, 18, 24, and 30 min of ventricular fibrillation. In all nonsurvivors, it was impossible to maintain diastolic pressure above 30 mm Hg even with large doses of epinephrine and saline. Maintenance of an adequate diastolic blood pressure during CPR appears important for survival.