Abstract: The flow fields in a partially stenosed artery with a complete bypass graft are investigated by numerical methods. The host artery with different severity of occlusions, including 0%-, 70%-, 80%-, 90%- and 100%-area stenosis, are included in current simulations, from which the influences of occluded severity on the flow structures in host artery as well as in bypass graft are emphasized. The results show that the flow features, including recirculation, vortex motions, and shear stress distributions on artery walls, are very sensitive to the stenosed severity. These results provide helpful information for further attacking the exact factors to cause the restenosis in the host artery with bypass graft implantation. [Copyright &y& Elsevier]