OBJECTIVE Surveillance protocols of infrainguinal vein bypass grafts have almost universal acceptance. To date corresponding studies of prosthetic grafts have not been carried out. We have performed a prospective 4-year duplex scan follow-up on polytetrafluoroethylene grafts to assess the usefulness of a surveillance program of prosthetic bypass grafts in preventing graft failure. METHODS Over 4 years 69 infrainguinal polytetrafluoroethylene grafts in 56 patients were studied at six monthly intervals by our vascular laboratory. Full duplex scan mapping of the grafts and inflow and outflow arteries and standard ankle pressure measurements were performed. A midgraft peak flow velocity was also measured. RESULTS Over 4 years 27 (39.1%) grafts occluded without any predictive changes in the preceding duplex scan examination. Of the 42 (60.9%) grafts that remained patent, only four developed stenoses (three at the proximal anastomosis and one at the distal anastomosis) that were amenable to intervention. Changes in ankle pressures or midgraft flow velocity did not predict failure. CONCLUSIONS The low yield of remediable disease does not justify the cost of duplex scan surveillance of infrainguinal prosthetic bypass grafts.