STI were measured on the 7th day after acute myocardial infarction in 144 male patients. These patients were reviewed at 6 weeks and 86 were reinvestigated and reviewed at 6 months. The STI could not predict the patients who would have either angina or a further myocardial infarction. Left ventricular function, as measured by STI, appeared to be a minor factor governing return to work after myocardial infarction. Patients who had developed ventricular aneurysms at 6 months had significantly increased EMI at 6 weeks. STI on day 7 had considerable prognostic significance for left ventricular failure at 6 weeks and death between day 7 and 6 weeks and it is suggested that LVET index could be usefully, and easily, introduced as a parameter after myocardial infarction.