Data are given for a 2-year study of fire department ambulance runs in Houston, Texas. Comparisons are made between those runs in which telemetry was used and those in which telemetry was not used. These data show an important relationship between the prognosis of patients who were recognized by emergency medical technicians as cardiac emergencies (and therefore received telemetry service) and those patients who were not identified as cardiac emergencies and did not receive telemetry service. Criteria used for clinical assessment and classification of emergencies are discussed. Emergency life-support systems with telemetry can have significant benefit for certain selected acute, recognizable cardiovascular emergencies, but the majority of ischemic heart disease fatalities do not appear to be deriving benefit from these systems.