Of 6,504 consecutive patients who underwent isolated coronary bypass grafting in 1985 to 1987, 72 (1.1%) patients experienced sternal wound complications. Ten patients (14%) with wound complications died of multi-system failure. Only the patients with negative cultures fared well; of the bacterial culture categories, polymicrobial infection carried the worst prognosis. Effects of recurring infection were seen throughout the first year. Patients, grouped according to conduits received, experienced these wound complication rates: vein grafts only, 11/1,085 (1.0%); one internal thoracic artery, 38/4,073 (0.9%); and bilateral internal thoracic artery grafts, 23/1,346 (1.7%). There were no significant differences in wound complication rates between primary and reoperation patients or among conduit groups. By logistic regression analysis, the relative risk for patients with diabetes and bilateral internal thoracic artery grafting was 5.00 (95% confidence interval, 2.4 to 10.5). Operation time as a continuous variable increased the relative risk of wound complication 1.47 times per hour (1.3 to 1.7); obesity, 2.90 times (1.8 to 4.8); and blood units as continuous variable, 1.05 times per unit (1.01 to 1.10). Bilateral internal thoracic artery grafting in nondiabetic patients carried no greater risk of wound complication than that in patients with vein grafts only or with one internal thoracic artery graft.