A new noninvasive temporary cardiac pacemaker-monitor has been developed to stimulate effective ventricular contraction in ventricular asystole or symptomatic bradycardia. It is quickly and easily applied, safe, and well tolerated even in conscious patients. It produced electrical cardiac responses in 105 of 134 patients; almost all of the remaining 29 patients were severely hypoxic. Stimulation was clinically useful in 82 patients: 20 of 43 were resuscitated from emergency arrest and 23 of 26 from expected arrest; 38 of 40 were successfully treated in readiness for an expected arrest that did not materialize; and one of nine patients with tachycardia was tested noninvasively for likelihood of recurrent ventricular tachycardia.