Based on both animal studies and field studies of the process and intermediate outcomes related to cardiopulmonary resuscitation (CPR), we initiated a randomized trial of dispatcher-assisted CPR, with the intervention arm receiving instructions for chest compression only and the control arm receiving standard instructions for airway maintenance, ventilation, and chest compression. Of 241 patients randomized to chest compression instructions only, 35 survived (14.6%) compared with 29 of 279 (10.4%) patients in the control arm (p = .09). These results may have implications for future guidelines and teaching CPR.