We assessed the impact of preoperative diameter of the venous conduit on reintervention rate and outcome following infrainguinal vein graft bypass. Consecutive infrainguinal vein bypasses between January 2001 and December 2006 were reviewed. All patients underwent preoperative measurement of vein graft diameter (VGD). Grafts were classified into those with VGD <3.5 mm and those with VGD >= 3.5 mm. All patients were enrolled in a duplex surveillance program. The association between VGD and reintervention rate was assessed. Graft patency and amputation rates were compared. There were 377 bypasses followed up for a median of 23 months (range 867). VGD was <3.5 mm in 139 grafts (36.9%) and >= 3.5 mm in 238 grafts (63.1%). A higher proportion of smaller vein grafts (32.3%) required reintervention to maintain graft patency compared with larger conduits (20.2%) (chi(2) = 7.7, p < 0.001). VGD (odds ratio [OR] = 2.87, 95% confidence interval [CI] 1.63-3.81; p < 0.001), smoking (OR = 1.83, 95% CI 1.39-3.20; p = 0.02), and type of bypass (OR = 1.86, 95% CI 1.49-2.47; p = 0.02) were variables associated with higher reintervention rate. There was no difference in graft patency (p = 0.13) or amputation rates (p = 0.35) between the two groups. Use of smaller vein grafts was associated with a higher reintervention rate. Provided that these grafts are surveyed and where necessary repaired, the use of smaller vein grafts is successful and expands the availability of autogenous conduit for infrainguinal arterial reconstruction.