Increasing number of coronary artery bypass surgery has been performed utilizing more arterial grafts because of poor long term patency rate of saphenous vein grafts. The risk of bilateral internal mammary artery grafting was studied in two groups of patients who were matched for recognized risk factors such as year of operation, age, gender, extent of coronary artery disease, left ventricular function, completeness of myocardial revascularization, and history of congestive heart failure. The patient groups differed in the fact that they received on internal mammary artery graft or two internal mammary artery grafts. The operative mortality rate was zero in either group. Analysis of operative and postoperative morbidity demonstrated no significant differences except for a slight increase in transfusion requirement, rate of wound infection and use of catecholamine in the group receiving two internal mammary artery grafts (p = 0.1, 0.1 and 0.05, respectively). We conclude at this moment that bilateral internal mammary artery grafting does not increase surgical mortality but increases the use of catecholamine comparing with the ipsilateral internal mammary artery grafting. Since the cases analysed in this study are limited, definitive conclusion should be deferred.