One-hundred thirty mobile intensive care unit paramedics were trained in the technique of direct laryngoscopic endotracheal intubation of cardiac arrest or deeply comatose patients. Three attempts at intubation were permitted. Of the 779 patients studied, 701 (90.0 percent) were successfully intubated: 57.9 percent on the first attempt, 26.1 percent and 5.5 percent on the second and third respectively. Reported and observed complications of the procedure numbered 74 (9.5 percent) of the 779 patients included in the study. There were three unrecognized esophageal intubations. The success rate rose to more than 94 percent toward the end of the study. It is concluded that endotracheal intubation of deeply comatose patients is a field procedure safely and skillfully performed by well-trained and monitored paramedical personnel, with success and complication rates at least comparable to other invasive airway techniques.