This study examined the relationship between graft diameter and subsequent patency in 79 patients who received Dacron aortobifemoral bypass grafts for aortoiliac occlusive disease between 1985 and 1989. Sixty-five percent of these patients were men, 25% were diabetic, and 94% were smokers, with an average age of 62 years. Patients were followed for a mean interval of 24 months. Life-table survival was 92% at 3 years. All surviving patients showed "significant" postoperative improvement by use of Society for Vascular Surgery/International Society for Cardiovascular Surgery combined clinical and vascular laboratory criteria. There were three early and five late graft thromboses. Primary and secondary life-table patencies were 85% and 92%, respectively, at 3 years. Dacron bifurcation grafts were selected to match the size of native arteries. Patients receiving small diameter grafts, defined as 12 mm (n = 9) and 14 mm (n = 39), were compared with patients receiving large diameter grafts of 16 mm (n = 26) and 18 mm (n = 5). Small diameter grafts were more likely to be used in women (p less than 0.01), but patient groups were otherwise comparable with respect to age, smoking history, diabetes, outflow status, operative indications, type of proximal anastomosis (end-to-end or end-to-side), location of distal anastomosis (common femoral vs deep femoral), type of graft construction (knitted vs woven), and functional result. Graft diameter did not influence life-table patency, which was 84% for small and 87% for large diameter grafts at 3 years (p = 0.74). Furthermore, none of the other variables listed above influenced graft patency.(ABSTRACT TRUNCATED AT 250 WORDS)