Left ventricular volume and ejection fraction were measured by 2-dimensional echocardiography from 2 orthogonal apical long axis views in 90 patients admitted with acute transmural myocardial infarction. Results were correlated with worst Killip class during hospital stay, enzymatic infarct size (peak CK-MB) and mortality. We used two algorithms, a biplane area-length algorithm and a modification of Simpson's rule. Both algorithms yielded essentially the same results: there were statistically significant trends towards higher end-diastolic and end-systolic volumes and lower ejection fraction with higher Killip -class. Ejection fraction was lower (P less than 0.01) in the 6 patients dying from cardiogenic shock (28.0 +/- 7.8% v. 46.6 +/- 10.1% in survivors with the area--length algorithm; 28.1 +/- 6.2% v. 48.1 +/- 10.2% with modified Simpson's rule). In 5 patients dying from other causes ejection fraction was 46.0 +/- 14.9% with the area-length method or 46.2 +/- 14.5% with Simpson's rule (not different from survivors). Correlation with peak CK-MB was only modest, though statistically significant: the regression equation was: y = -0. 39x + 54 (r = -0.35; P less than 0.01) with the area-length method; and y = -0. 41x + 55 (r = -0.37; P less than 0.01) with Simpson's rule. Left ventricular ejection fraction measured at the bedside in patients with acute myocardial infarction, can provide useful clinical information. Patients likely to develop shock can be identified shortly after admission.