The value of alpha adrenergic agents in reversing asphyxial circulatory arrest has been documented. A study was undertaken to determine the effect of alpha adrenergic stimulation on central diastolic pressure during carch'opulmonary resuscitation (CPR). Rate of successful resuscitation and time to resumption of spontaneous circulation were also examined. Fourteen anesthetized dogs were subjected to asphyxia-induced circulatory arrest. Five minutes after cessation of circulation, manual chest compression and ventilation with oxygen were begun. Electrocardiogram, aortic and central venous pressures were recorded continuously. CPR was performed for 10 minutes or until spontaneous circulation resumed. Six experimental animals received 5 mg of intravenous phenylephrine after 60 seconds of CPR. Eight control dogs received no drug. All animals showed electromechanical dissociation throughout the arrest period. Two control animals were resuscitated in less than 60 seconds, and were thus eliminated from the experiment. Six (100%) of the dogs receiving phenylephrine were resuscitated successfully, in an average of 75 seconds. In this group, aortic diastolic pressure averaged 55.8 mm Hg just prior to resumption of spontaneous circulation. Of six control dogs, only two (33%) were resuscitated in an average of 240 seconds. Aortic diastolic pressure in these resuscitated controls averaged 23.7 mm Hg just prior to resumption of circulation. These differences in time to resuscitation and diastolic pressures preceding resuscitation were significant (P < .01 and P < .02 respectively). Ten dogs were successfully resuscitated, with an average diastolic pressure of 43 mm Hg just prior to resuscitation. Highest diastolic pressure during CPR in the four animals not resuscitated averaged 11.25 mm Hg. This difference was also significant (P < .02). These results demonstrate that phenylephrine, an alpha adrenergic agent, augments aortic diastolic pressure during CPR. This increase in diastolic pressure is shown to correlate with improved rate and time of successful resuscitation from asphyxial arrest in a canine model.