Rates of coronary restenosis after stent implantation vary with stent design. Recent evidence suggests that alterations in wall shear stress associated with different stent types and changes in local vessel geometry after implantation may account for this disparity. We tested the hypothesis that wall shear stress is altered in a three-dimensional computational fluid dynamics ~CFD! model after coronary implantation of a 16 mm slotted-tube stent during simulations of resting blood flow and maximal vasodilation. Canine left anterior descending coronary artery blood flow velocity and interior diameter were used to construct CFD models and evaluate wall shear stress proximal and distal to and within the stented region. Channeling of adjacent blood layers due to stent geometry had a profound affect on wall shear stress. Stagnation zones were localized around stent struts. Minimum wall shear stress decreased by 77% in stented compared to unstented vessels. Regions of low wall shear stress were extended at the stent outlet and localized to regions where adjacent axial strut spacing was minimized and the circumferential distance between struts was greatest within the stent. The present results depict alterations in wall shear stress caused by a slotted-tube stent and support the hypothesis that stent geometry may be a risk factor for restenosis by affecting local wall shear stress distributions. © 2003 Biomedical Engineering Society.