The atrioventricular (AV) plane displacement was studied by echocardiography in 79 subjects (45 healthy subjects and 34 patients with acute myocardial infarction or chronic congestive heart failure). From apical 4- and 2-chamber views the displacement of the AV plane towards the apex in systole was recorded at 4 sites in the left ventricle (LV) corresponding to the septal, anterior, lateral, and posterior walls and the mean value from the above 4 sites (AV-mean) was calculated. In addition, in healthy subjects, the AV plane displacement at right ventricular free wall was also recorded. The AV-mean correlated well with the echocardiographic ejection fraction determined by biplane area-length method (r = 0.96, P less than 0.001). The correlation was also high when the percentage of the left ventricular shortening along the long axis was used (r = 0.97, P less than 0.001). The correlation between ejection fraction and AV-mean was also good when separate analysis was made for the subjects with preserved ejection fraction (r = 0.86, P less than 0.001) and decreased ejection fraction (r = 0.82, P less than 0.001). The right ventricle had a significantly higher AV plane displacement (P less than 0.001) than the LV. The study also includes determination of the muscular excursions of the septal and posterior walls along the short axis of the left ventricle from the parasternal long axis view. The AV plane displacement of the respective walls was relatively greater (P less than 0.001) compared to concentric contractions. The septal and posterior wall excursions along the short axis correlated poorly with the AV plane displacement of the respective walls (r = 0.55, P less than 0.01 and r = 42, P less than 0.05).