Coronary artery bypass graft (CABG) is a routine surgical treatment for ischemic and infracted myocardium. A large number of CABG fails postoperatively due to intimal hyperplasia within months or years. The cause of this failure is thought to be partly related to the flow patterns and shear stresses acting on the endothelial cells. An accurate representation of the flow field and associated wall shear stress (WSS) requires a detailed three-dimensional (3-D) model of the CABG. The purpose of this study is to present a detailed analysis of blood flow in a 3-D aorto/left CABG, bypassing the occluded left-anterior descending coronary (LAD) artery. The analysis takes into account the influence of the out-of-plane geometry of the graft. The finite volume technique was employed to model the 3-D blood flow pattern to determine the velocity and WSS distributions. This study presents the flow-field distributions of the velocity and WSS at four instances of the cardiac cycle, two in systole and two in diastole. Our results reveal that the CABG geometry has a significant effect on the velocity distribution. The axial velocity profiles at different instances of the cardiac cycle exhibit strong skewing; significant secondary flow and vortex structures are seen in the in-plane velocity patterns. The maximum WSS on the bed of the occluded LAD artery opposite to the graft junction is 14 Pa in mid-diastole while there is a significantly lower and more uniform distribution of WSS on the bed of the anastomosis. The present results indicate that non-planarity of the blood vessel along with the inflow conditions have a substantial effect on the fluid mechanics of CABG which contribute to the patency of graft.