In a prospective study, we assessed the diagnostic and therapeutic applications of intraoperative angioscopy for peripheral vascular procedures. Sixty-seven vessels and 17 bypass grafts were examined with a flexible, multichannel, fiberoptic endoscope (outer diameter 2.8 mm), with video projection of a magnified image used during the following operations: femoropopliteal or femorotibial bypass (14), aortofemoral (six), axillopopliteal bypass (one), and femoral embolectomy (three). Preoperative angiograms were compared with the findings at prebypass intraoperative angioscopy. Immediately after bypass, angioscopic appearances of the graft, anastomosis, and distal runoff artery were compared with a completion angiogram. Significant disparity between angioscopy and arteriography occurred in five patients (21%), with resultant change of management in three (12.5%). In comparison to angioscopy, the arteriograms gave a false negative rate of 12.5% (3 of 24) and a false positive rate of 8% (2 of 24). Angioscopy was accurate for assessment of anastomoses in all cases and was particularly beneficial for monitoring balloon catheter embolectomy. Complications were limited to three instances of vasospasm when the scope was used in narrow vessels. No embolization, intimal trauma, infection, or vessel perforation occurred. We conclude that angioscopy promises to be a safe and accurate alternative technique for intraoperative assessment, monitoring anastomotic results and controlling therapeutic procedures.