BACKGROUND Left ventricular dilatation and a low ejection fraction after acute myocardial infarction are independent indicators of a poor prognosis. ACE inhibitors have been shown to decrease left ventricular dilatation after myocardial infarction. In the GISSI-3 trial, patients were randomly assigned, within 24 h of onset of myocardial infarction symptoms, to 6 weeks of treatment with lisinopril, nitroglycerin, both or neither, in an open, 2 x 2 factorial design. The study showed that early treatment in relatively unselected patients with lisinopril decreases mortality at 6 weeks and severe left ventricular dysfunction. We assessed (1) the prognostic value of pre-discharge 2-D echocardiographic variables, and (2) the effects of lisinopril on the progression of left ventricular dilatation. RESULTS 2-D echocardiograms were available pre-discharge in 8619 GISSI-3 trial patients discharged alive. In 6405 of these patients, a 2-D echocardiographic study was also available at 6 weeks, and at 6 months. Pre-discharge end-diastolic and end-systolic volumes, and ejection fraction predicted 6-month mortality and non-fatal clinical congestive heart failure (P < 0.01). The increase in left ventricular volumes over time was significantly reduced by 6 weeks' lisinopril treatment in patients with wall motion asynergy pre-discharge of > or = 27%. Patients with wall motion asynergy < 27% showed no dilatation and lisinopril did not affect volumes at 6 months. Patients randomized to lisinopril also had smaller volumes after withdrawal of treatment at 6 weeks. Lisinopril did not affect left ventricular ejection fraction. CONCLUSIONS 2-D echocardiography independently contributes to pre-discharge risk stratification in terms of 6-month mortality and clinical heart failure after myocardial infarction, and early, short-term treatment with lisinopril in unselected myocardial infarction patients attenuates left ventricular dilatation; an effect evident in patients with larger infarcts. These results probably only partly explain the effect of lisinopril on total mortality concentrated in the first week after infarction.