An overview of a total of 135 in situ femorocrural bypass operations is given. In the operations all grafts were anastomosed distally to the infrapopliteal arteries: to the proximal half of the crural vessels 52 times and to the distal half 83 times. The indication for surgery was critical limb ischaemia. In addition to routine intraoperative angiography, orthograde angioscopy of the graft was carried out to assess the completeness of valvulotomy in 96 patients (group A). In 39 patients (group B) for whom an endoscope was not available, completion angiography was conducted to ensure graft integrity. The two groups were comparable with respect to their composition. On the basis of the endoscopic findings, revisions were performed in 17 patients with incomplete valve ablation in group A, whereas in group B there were no interventions (P < 0.01, chi 2 test). Using life-table analysis, cumulative primary patency rates for groups A and B were 76% and 76% at 30 days, 62% and 44% at 1 year and 43% and 27% at 4 years, respectively. By comparison with the log rank test, a significant difference in patency among both groups could not be established (P = 0.18).