In 28 patients with the left internal mammary artery (IMA) used as a sequential coronary artery graft, clinical and angiographic evaluation was made 19-47 months postoperatively. Patency was 96% in the proximal anastomoses and 93% in all the anastomoses. Angiography, however, showed optimal function in only 75% of the distal graft ends. These observations indicate that routine use of left IMA as a sequential graft should be restricted to experienced surgeons. Clinical and angiographic findings did not always correlate, emphasizing that evaluation of IMA-graft patency should include angiography.