The governing equations for pulsatile fluid flow were solved in their finite volume formulation in order to simulate blood flow in a variety of three-dimensional aneurysm geometries. The influence of geometric factors on flow patterns and fluid mechanical forces was studied with the goal of identifying the risk of aneurysm rupture. Aneurysm morphology was characterized by quantitative shape indices reflecting the three dimensionality of the vasculature derived from clinical studies. Recirculation zones and secondary flows were observed in aneurysms and arteries. Regions of extreme and alternating shear stress were observed and identified as sites for potential aneurysm rupture. The ellipticity of an aneurysm was observed to be strongly correlated with wall shear stress at the aneurysm fundus, while its non-sphericity, volume, and degree of undulation were more weakly correlated.