When failure of vein grafts is due to technical error it is usually observed in the early postoperative period. In this review we describe late failure of five bypass grafts as a result of entrapment of the vein graft caused by an improperly placed tunnel from the femoral to the popliteal artery. Vein graft entrapment may either produce no symptoms or eventually lead to limb ischemia. Pulses and pressures that vary with flexion and extension maneuvers should alert the clinician to the possibility of an entrapment syndrome. The characteristic arteriographic findings observed in these patients include an aberrant course of the vein graft outside the anatomic course of the popliteal artery and position-dependent compression of the graft. The ability of magnetic resonance angiography to demonstrate the arteriographic appearance of the graft as well as the precise location of the compression and to identify structures involved in the entrapment, make it a valuable noninvasive tool in the preoperative assessment of these patients. Treatment options include division of the gastrocnemius muscle, division of the vein graft, or replacement of the vein graft. Familiarity with vein graft entrapment should facilitate its recognition. Careful placement of bypass grafts along the anatomic course of the popliteal artery within the popliteal space will prevent this complication.