Postoperative bypass surveillance can identify graft-related stenoses in 25% of grafts during the first two years after surgery. Correction of the stenoses before they lead to graft occlusion improves the patency significantly. Clinical assessment including distal pressure measurements is of poor sensitivity. Surveillance is best performed with color duplex scanning. Ideally, grafts are examined first after one to two months, thereafter every three months and, after one year, at intervals of six months. Graft surveillance beyond two years is hardly justified, as is the case with prosthetic grafts. Symptom-producing and tight stenoses should be corrected. Percutaneous transluminal angioplasty is appropriate for short stenoses, whereas stenoses longer than 2 to 3 cm are best treated surgically.