To increase the number of arterial grafts in patients with multivessel coronary disease, we have used branches of the left internal mammary artery (LIMA) as bypass grafts. From March 1990 to June 1993, 15 patients (13 males and 2 females) aged 38 to 65 years (mean 57 +/- 8), received a total of 30 LIMA branch anastomoses. The two terminal branches were used to perform a "Y" graft to the left anterior descending coronary artery territory in 13 patients. A pericardiophrenic branch was used in four cases. Five patients (33.3%) had complete myocardial revascularization using IMA only. There were neither early nor late deaths and all patients are free from angina at a mean follow-up of 20 months (6 to 45 months). However, early postoperative cardiac catheterization, performed in 12 patients (80%), revealed a 20% occlusion rate for each terminal branch and a 50% occlusion rate for the pericardiophrenic branch. Technically challenging due to the small diameter of the grafts, the terminal LIMA branches should be limited to selected patients when more conventional arterial or vein conduits are not available. More proximal branches have a higher occlusion rate and their use is not recommended.