A cohort of 610 well-characterized patients undergoing coronary artery bypass grafting were followed through the first postoperative year. Graft patency was angiographically assessed in 578 (94.8%) of the patients on average 12.1 (SD 1.5) months postoperatively and was related to characteristics of grafts and patients. For internal mammary artery grafts the incidence of graft occlusion was higher in women than in men and was inversely related to body surface area. In multivariate analysis the influence of gender was no longer significant when adjusted for body surface area. With vein grafts the incidence of occlusion was inversely related to body surface area and was positively associated with ejection fraction. Occlusion of vein grafts was less common in patients treated with beta-blockers pre- and peroperatively.