A method of measuring the displacement of the atrioventricular (AV) of the left ventricle plane during the cardiac cycle in 71 healthy persons is described. An echocardiographic equipment with two cursors was used. Measurements were performed from four sites in the AV plane situated about 90 degrees apart and corresponding to the septal, anterior, lateral and posterior myocardial walls. The mean displacement during systole was 16 mm towards the apex. There was no significant difference in the recordings from the four sites. The study population was divided into three groups with mean ages 28, 42 and 60 years (group I, II and III). The displacement was significantly smaller in group III compared with groups I and II. Fractional shortening, however, could not demonstrate such a difference. The determination of displacement of the AV plane may imply the introduction of a new and simple method in assessment of left ventricular function.