Animal models of peripheral nerve ischemia have yielded variable results. The question of whether post-ischemia re-establishment of blood flow to the nerves augments injury has not been examined. To study this question, the ipsilateral common iliac and femoral arteries were occluded with arterial snares for 3 hours in rats; 14C-butanol tissue distribution was then used to measure blood flow in both sciatic and posterior tibial nerve trunks and in both biceps femoris muscles during occlusion and reperfusion. Clinical limb function was graded serially, with the undisturbed contralateral limb serving as the study control. Nerve blood flow was reduced throughout the ischemic period and was only 20% of the control value in the posterior tibial nerve. Muscle blood flow was unchanged. All rats had functional impairment, with an average limb function score of 7.5 (normal score < 2). During reperfusion, blood flow in the distal sciatic and posterior tibial nerves was approximately double that of control nerves at 2 hours, and muscle blood flow was also elevated. At 21 hours, tibial nerve blood flow was still twice that of the control nerve, but flows in the distal sciatic nerve and muscle were unchanged from control levels. Clinically, limb function improved progressively after reperfusion. It was concluded that nerve ischemia is attended by a relatively prolonged hyperemic flow response during reperfusion.