Local blood flow in the forefoot (SBF) was measured continuously during 24 hours by 133xenon clearance technique in 10 patients prior to and at least 1 year after successful reconstructive vascular surgery for severe arterial insufficiency (mean: 18 months, range: 12-36). A group of 10 patients with normal peripheral circulation served as a control group. In spite of a considerable increase of the ankle/arm systolic blood pressure index--preoperative: 0.30 +/- 0.12, postoperative: 0.78 +/- 0.28 (mean +/- 1 SD)--the SBF decreased by 50% (p less than 0.001) following reconstructive vascular surgery during day activities. During sleep, however, SBF increased by 80% (p less than 0.001). The relative changes in SBF from day to night at the postoperative examination did not differ from that of the control group, i.e., the normal 24-hour blood flow pattern had been obtained. These changes in SBF are explained by the reappearance of peripheral vasoregulatory mechanisms. Postreconstructive hyperemia was evaluated by the same technique. The changes in SBF following surgery in the positions supine, awake and supine, asleep were found to be insignificant (0.80 less than p less than 0.90). It is concluded that the long-term postreconstructive hyperemia merely is a reflection of the normal 24-hour blood flow pattern.