Left ventricular asynergy associated with acute myocardial infarction was evaluated by crosssectional echocardiography. Patients with acute infarction were studied within 48 hours of admission, and a segmental analysis of left ventricular wall motion was performed using nine segments obtained by short- and long-axis recordings of the left ventricle. By this segmental approach, analysis of wall motion in the entire left ventricle was possible. Complete studies were recorded in 37 of 44 original patients. Segmental wall motion abnormalities were recorded and localized in each of the 37 study patients. Asynergy was detected in 142 segments, and 29 patients had multiple segment involvement. Asynergy was most common in the apical segments of the left ventricle, but the cross-sectional scans permitted detection of asynergy in all segments. Correlation between the ECG and the cross-sectional echocardiogram revealed that 19 of 20 patients with inferior infarction had asynergy in posterior segments, 14 of 14 patients with anterior infarction had asynergy in anterior segments, and three of three patients with anteroinferior infarction had asynergy both anterior and posterior segments. In addition, the location of segmental asynergy followed specific patterns for each ECG subgroup of infarction. In four patients with postmortem examination, 21 of 22 segments that had asynergy by cross-sectional echocardiography also had pathologic evidence of infarction. Therefore, the cross-sectional echocardiogram provides a reliable method for detecting the presence and location of regional asynergy associated with acute myocardial infarction.