Left ventricular function was evaluated with serial recording of STI intervals in 78 patients with stable angina on effort undergoing coronary and left ventricular cineangiography. On the basis of these data the patients were divided into four groups: OV) nor or mild coronary disease (n. 11); 1V) 70% stenosed vessel; 2V) two significantly affected vessels (n. 32); 3V) three significantly affected vessels (n. 18). Thirty-six patients (9 with one stenosis, 17 with 2, 10 with 3) underwent coronary artery bypass. Thirty-one 8 with one, 15 with 2, 8 with 3) refused the treatment in spite of the same clinical situation and were medically treated. Recordings were performed before medical and surgical treatment and after 6 and 12 months. Initial average values of the patients of 2V and 3V groups showed a shorter LVETI, longer PEPI and higher PEP/LVET ratio than those of 1V and 0V groups. Subjects of 2V group and abnormal left ventricular wall motion showed longer PEPI and higher PEP/LVET than patients of 2V without abnormal wall motion. On first evaluation no differences were observed between surgical and medical groups. The latter did not show any difference after 6 and 12 months. Surgical patients of 2V and 3V showed a longer LVETI, shorter PEPI and a lower PEP/LVET than the medical group. In the surgical group PEPI and PEP/LVET were significantly decreased after surgery while LVETI was prolonged. Our results suggest an improvement of left ventricular performance by coronary artery bypass in patients with coronary artery disease.