Early diagnosis of acute myocardial infarction is important to enable myocardial injury to be limited by means of various treatments. Monitoring of vessel patency with vector cardiography or continuous 12-lead ECG recording is a form of surveillance that has been widely accepted in Sweden. In post-reperfusion therapy monitoring, there is approximately 80 per cent agreement between monitoring ST-segment changes and acute coronary cardiography. For risk stratification of patients with unstable angina or non-Q-wave infarction, ST-segment monitoring manifests great predictive power which is further enhanced by its combination with the measurement of highly specific markers of myocardial injury. Computerised techniques for continuous monitoring of multiple ECG leads have contributed much to our understanding of the dynamics of acute coronary heart disease. Valuable prognostic information is available in real time, early identification of myocardial injury is possible, and treatment strategies can be based upon more reliable grounds.