We used fluorescein dye to evaluate the vascularity of flaps in 73 patients and of the left colon in 23 individuals after resection and replacement of the abdominal aorta. Instant photographs of the dye pattern were taken in the light using a specially modified Polaroid camera. All areas of skin and bowel that showed adequate staining with the dye survived, and all but one of ten areas that were nonfluorescent became necrotic unless they were excised or revascularized. The intraoperative use of fluorescein dye with the fluorescence camera is a useful technique for all surgeons who need to evaluate the vascularity of tissue.