The efficacy of mammary artery bypass for coronary artery disease has been well established. The present retrospective series of consecutive patients was scrutinized to assess the incidence of sternal dehiscence following myocardial revascularization using the right and left internal mammary arteries. For comparison, the consecutive group of patients undergoing myocardial revascularization with unilateral internal mammary artery bypass was analyzed for similar sternal complications. In a consecutive series of patients, 277 patients underwent myocardial revascularization using the right and left internal mammary arteries for bypass. The overall operative mortality in this group of patients was 0.722 per cent. In this group there was an overall incidence of seven sternal dehiscences, both partial and complete for an incidence of 2.52 per cent. Upon analysis, it was shown that the female sex and diabetes were the conditions that most likely predisposed to the occurrence of sternal dehiscence whether partial or complete. For comparison, a consecutive group of 413 patients were analyzed for similar demographic data and results. The overall operative mortality in this group was 1.21 per cent. The overall incidence of sternal dehiscence both partial and complete, was 0.484 per cent. Both instances of sternal dehiscence occurred in diabetic patients and the data indicates, as in the bilateral internal mammary artery group, the presence of diabetes predisposed to the occurrence of this complication. The low overall incidence of sternal dehiscence in the expanded use of the mammary arteries should not deter the surgeon from aggressive use of the mammary arteries. One should use caution, however, in using bilateral mammary artery grafts in diabetics, women, and to a lesser extent, patients more than 70 years of age.