30 coronary artery disease (CAD) patients (pts) were studied by echocardiography before and after left anterior descending (LAD) coronary bypass graft in order to evaluate left ventricular (LV) behaviour. Echocardiograms were recorded early pre- (48 hours) and post-operatively (mean 12 days) and at a mean distance of 12 months (6 to 15) after operation. The following parameters were considered: left ventricular end diastolic dimension (LVDD), right ventricular diastolic dimension (LVDD), right ventricular diastolic dimension (RVDD), diastolic thickness, systolic thickening and motion of the interventricular septum (IVS) and of the LV posterior wall (LVPW). 21 pts (70%) showed reduced systolic thickening (RST less than or equal to 30%) and 17 (57%) reduced systolic motion (RSM less than or equal to 3 mm) of the septum. Before surgery no patient showed IVS paradoxical movement, left bundle branch block, valvular regurgitation, shunt, LV aneurysm. A previous myocardial infarction was present in the story of 7 pts: anterior location in 4 pts, inferior in 3 pts. Soon after operation (mean 12 days) 4 pts showed normal IVS motion; in 7 pts it was reduced (less than or equal to 3 mm) and in 19 IVS was paradoxical. In 15 pts of this last group LVPW motion resulted remarkably increased after the bypass graft. The other echo parameters didn't show significant variation. Averaging 12 months after operation, IVS systolic thickening resulted normal in 21 of the 30 pts. (70%); in 14 of the last group of 21 there was a RST preoperatively. IVS motion resulted normal in 21 of the 30 pts (70%), reduced in 5 (17%), paradoxical in 4 (13%). LVPW motion returned to the preoperative value in all but 3 pts, in whom it remained elevated. The other echo parameters didn't show any significant variation. We conclude that: 1) IVS paradoxical motion is frequently recorded by echo shortly after coronary bypass graft surgery. 2) In most pts it is accompanied by an increased excursion of LVPW, probably compensatory in origin. Both tend to normalize within few months in most of the subjects.