In 305 patients operated upon for symptomatic ischaemic heart disease, a series of resting electrocardiograms, obtained during the first days after operation, was evaluated. A new Q wave was found in 10% of the patients. The genesis of this EGG change had not correlation with the patients' age and sex, presence of hypertension and diabetes mellitus, tobacco smoking, blood cholesterol level, functional calss of angina pectoris, previous myocardial infarction, the number of affected coronary arteries, duration of extracorporeal circulation or anoxic circulatory arrest, and peroperatively measured graft blood flow. A new Q wave after revascularization occurred more frequently in patients with multiple venous aortocoronary bypasses. The new Q wave is an EGG manifestation of myocardial necrosis with subsequent local disturbance of left ventricular function.