The impact of improvements in prehospital cardiologic service on total and prehospital mortality associated with acute coronary insufficiency (ACI) and acute myocardial infarction (AMI) and the causes of fatal outcomes is illustrated by a study based on the acute myocardial infarction register involving populations from two city districts between 20 and 69 years of age. Prehospital mortality caused by ACI and AMI is shown to decline with the progress of cardiologic care. The decline is attributed to reduced incidence of some causes of death, such as heart failure and cardiogenic shock. Sudden coronary death (85.1%) remains the principal cause of prehospital mortality.