An external cardiac pacemaker-monitor has been developed that provides safe, effective noninvasive ventricular stimulation that is well tolerated in conscious patients and allows clear recognition of electrocardiographic response. The noninvasive temporary pacemaker (NTP) has now been applied in 134 patients in five hospitals. Stimulation was tolerated well in 73 of 82 conscious patients, and nine found it intolerable. The NTP was effective in evoking electrocardiographic responses in 105 patients; the 29 failures were in the presence of prolonged hypoxia or severe discomfort. The NTP was clinically useful in 82 patients: 43 of 86 were resuscitated from emergency or expected arrest, 38 of 40 were maintained in standby readiness for up to 1 month but did not require stimulation, and one of eight patients with tachycardia obtained some clinical benefit. The NTP was especially useful in 25 patients with complications or contraindications to endocardial pacing and in 57 patients in whom insertion of an endocardial electrode was avoided.