The effect of monophasic blood flow on the patency of microvascular anastomoses in the rat femoral artery was evaluated by the authors. An experimental model of monophasic blood flow was created in the rat femoral artery to simulate that seen in patients with peripheral vascular disease. Microvascular anastomoses were performed, and the patency at the first hour and 24 hr later was determined. The studies demonstrated that microarterial anastomotic patency was the same when performed in vessels with monophasic or triphasic flow patterns. The authors conclude that monophasic blood flow is not an absolute contraindication for free-tissue transfer.