Thirty-seven patients undergoing femoropopliteal, fifteen undergoing femorodistal reconstruction and seven below knee amputees were subjected to prospective measurement of peripheral resistance. Resistance was significantly higher in the amputation and femorodistal groups than in the femoropopliteal group (P less than 0.03 and P less than 0.005 at 76 ml/min). In the femoropopliteal group patients with three vessel runoff had a significantly lower resistance than those with two or single vessel runoff (P less than 0.01). In the femoropopliteal group resistance of patent grafts at four months was significantly less than thrombosed grafts (P less than 0.006). Patients with a resistance less than 1200 mPRU had a significantly better patency than those in whom the resistance was greater than 1200 mPRU (P less than 0.05). Taking all the failed grafts there was a significant correlation between graft patency and resistance (P less than 0.003). Resistance measurement has been shown to correlate with the severity of the disease, with runoff defined radiographically and with graft patency. In a simplified form it may prove a useful adjunct to other methods of assessment in patients with distal disease.