The value of post-reconstruction intraoperative angiography after in situ saphenous vein bypass has not been clearly defined. A retrospective review of intraoperative completion angiography using a standard proximal bypass injection technique without inflow occlusion was performed on 298 in situ saphenous vein bypasses constructed over a 72-month interval to treat critically ischemic limbs. Abnormal operative angiograms were found on retrospective review in 55 cases (18%). Minor abnormalities such as distal arterial or vein conduit spasm (class I defects) were found in 26 bypasses (9%) and required no surgical intervention. An anastomotic buckle or extrinsic compression due to an adventitial band (class II defect) was seen in five bypasses (2%). Defects requiring a major surgical revision (class III) were seen in 24 instances (8%). These abnormalities included nine cases with intraluminal platelet thrombus and six with a significant anastomotic torsional abnormality. In addition, there were five bypasses anastomosed to unsuitable diseased segments of distal arteries. Three of 24 (12%) of the bypasses with class III angiographic abnormalities required further revision within the first month after surgery, after duplex scanning had identified hemodynamically significant abnormalities, compared with 14 of 274 (5%) early revisions of the remaining in situ bypasses. The 30-day primary patency rate for bypasses with class III angiographic abnormalities was 88%. This compares with a rate of 95% for the remaining bypasses. The difference was not statistically significant. The 30-day and 48-month secondary patency rates for bypasses undergoing an immediate intraoperative revision for a class III abnormality were 100% and 93%, respectively. These rates were equivalent to the secondary patency of the in situ bypasses without class III abnormalities. Although the incidence of significant (class II and class III) angiographic abnormalities was low (10%), these abnormal findings allowed immediate correction of a jeopardized bypass, with minimal sequelae.