Vascular surgery involves multiple transfusions with their concomitant hazards. At the start of each vascular procedure, 20 per cent of each patient's blood (approximately 1,000 of 5,600 ml) is removed and replaced with colloid and crystalloid and the withdrawn blood returned at the end of surgery. Theoretically, if 40 per cent of the blood volume (2,000+ ml) could be withdrawn, essentially no banked blood would be required for a major vascular procedure. Therefore, 40 per cent (900+ ml) of the blood volume of twenty greyhounds was withdrawn under anesthesia and replaced with stroma-free hemoglobin solution (SFHS). Abdominal aortic resection and graft replacement was performed, and any blood lost during the procedure was replaced with SFHS. After surgery the withdrawn blood was returned to the dog and excess volume removed with postoperative hemodilution diuresis. The study included a battery of twenty tests for monitoring during the procedure and at intervals from this project that in greyhounds 40 per cent or more of the blood volume may be removed and replaced with SFHS and major vascular surgery done without undue risk and with unaltered kidney function.