In a prospective series of 201 consecutive patients with creatine kinase-MB--documented acute myocardial infarction (AMI), postadmittance and predischarge echocardiographic wall motion indexes (WMI) were determined (median 45 hours vs 14 days after AMI). No significant change of left ventricular systolic performance was found between postadmittance and predischarge examinations in 179 survivors (WMI 1.3 +/- 0.4 vs 1.4 +/- 0.4, p greater than 0.05). Hospital mortality was 11% (22 of 201), cumulated 2-month mortality 15% (31 of 201) and cumulated 1-year mortality 26% (52 of 201). Mortality increased rapidly with decreasing left ventricular function as determined by WMI. When early WMI was less than 1.0, 1-year mortality was 51% (28 of 55) versus 8% (7 of 83) when WMI was greater than 1.3 (p less than 0.0001). Ventricular fibrillation (n = 24) and cardiogenic shock (n = 27) carried a much better prognosis when WMI showed good left ventricular function. When WMI was less than 1.0, 1-year mortality was 83% (10 of 12) versus 93% (13 of 14) in ventricular fibrillation and cardiogenic shock, respectively, whereas it was 0% (0 of 4) versus 33% (2 of 6) when WMI was greater than 1.3. In 15% of patients major discrepancies between early Killip class and WMI were noted. WMI showed much smaller fluctuations during the hospital course of AMI than did Killip class and appeared to be a more stable prognostic marker. Large-scale, early risk stratification by echocardiography has now become available and appears to facilitate a rational, individualized discharge policy in the coronary care unit and to provide an improved basis for randomization of patients in controlled studies aimed at tailoring new treatment in AMI.