Angiotensin converting-enzyme (ACE) inhibition reduces mortality among patients surviving an acute myocardial infarction, but whether to give ACE-inhibitors to all patients or target their use to selected patients is unclear. Seven thousand and one consecutive enzyme-confirmed myocardial infarctions were screened. One thousand seven hundred and forty-nine patients with echocardiographic signs of left ventricular dysfunction were randomized to oral trandolapril (876 patients) or placebo (873 patients) starting from days three to seven following the infarction. Average follow-up was 27 months. There were 304 deaths (34.7 percent) among patients on trandolapril vs. 369 deaths (42.3 percent) among patients on placebo (p = 0.0013). Relative risk (RR) of death in the trandolapril group was 0.78 (95% confidence interval (CD 0.67-0.91). Trandolapril reduced cardiovascular death (RR 0.75, CI 0.63-0.89) and sudden death (RR 0.76, CI 0.59-0.98). Progression to severe/resistant heart failure was reduced (RR 0.71, CI 0.56-0.90). Recurrent myocardial infarction (fatal or non-fatal) was not significantly reduced (RR 0.86, CI 0.66-1.13). It is concluded that long-term treatment with trandolapril in patients with reduced left ventricular function shortly after myocardial infarction significantly reduced total mortality. The substantial mortality risk reduction was obtained in 25% of consecutive patients screened for entry encouraging a selective use of ACE inhibition following myocardial infarction.