Claudication distance and maximum walking distance are both measures of disability. Estimates of the distances which a patient with intermittent claudication can walk are commonly used by vascular surgeons as surrogate measures of handicap. We studied how accurately distance was estimated by 70 patients with intermittent claudication, and by 100 British vascular surgeons. Patients and vascular surgeons estimated actual distances of 30 m and 34 m, respectively. Estimates were 46 m median (range 2.7-402 m) for claudicants, and 46 m median (range 15.2-186 m) for vascular surgeons, median over estimates of 52% and 34% respectively. Claudicants' errors can easily be eliminated by accurate and appropriate measurement of claudication and maximum walking distances but interpretation of the data by surgeons is dependent on their own ability to estimate distance. Flawed perceptions by patients and their surgeons of the disability of reduced walking distance illustrates the need for reliable measures of handicap on which to base therapeutic decisions in patients with intermittent claudication.