Wall　shear　stress,　as　one　of　the　most　important　hemodynamic　parameters　of　the　cardiovascular　system,　has　been　studied　extensively　in　the　numerical　and　experimental　approaches　to　blood　flow　in　various　arteries.　In　order　to　clarify　the　influence　of　graft　diameter　on　the　wall　shear　stress　in　a　femoral　two-way　bypass　graft,　the　pulsatile　blood　flows　in　two　models　were　simulated　with　the　finite　element　method.　Both　models　were　constructed　with　different　diameters　of　grafts.　The　main　geometric　structure　and　the　boundary　conditions　were　identical　for　both　models.　The　emphasis　was　on　the　comparison　analysis　of　wall　shear　stresses　in　the　vicinity　of　the　distal　anastomosis.　The　temporal-spatial　distributions　of　wall　shear　stresses,　wall　shear　stress　gradients,　and　oscillating　shear　index　were　analyzed　and　compared.　The　present　study　indicated　that　femoral　artery　bypassed　with　a　large　graft　demonstrated　relatively　uniform　wall　shear　stresses　and　small　wall　shear　stress　gradients,　whereas　it　does　not　have　advantages　in　the　oscillating　shear　index.　The　large　model　exhibits　better　and　more　regular　hemodynamic　phenomena　and　may　be　effective　in　decreasing　the　probability　of　the　initiation　and　development　of　postoperative　intimal　hyperplasia　and　restenosis.　Thus,　appropriately　large　grafts　are　applicable　in　the　clinical　practice　of　femoral　two-way　bypass　operation.　More　detailed　studies　are　necessary　on　this　problem　for　the　purpose　of　increasing　the　success　rates　of　the　femoral　bypass　grafts.　(c)　2005　IPEM.　Published　by　Elsevier　Ltd.　All　rights　reserved.