Background: The carotid bifurcation is one of the most susceptible locations for atherosclerotic plaques. It is important to assess wall shear stress (WSS) and blood flow patterns in this area. Purpose: To assess local WSS and blood flow patterns at the origin of the internal carotid artery (ICA). Material and Methods: Twenty-eight ICAs of 16 healthy volunteers were studied. A cine phase-contrast magnetic resonance (MR) sequence combined with a three-dimensional paraboloid model was applied to calculate WSS values and to obtain flow parameters. WSS spatial distribution features and local flow patterns were analyzed. Results: Mean WSS was 0.560 +/- 0.180 (range -0.745 to 3.563) N/m(2) at the origin of 28 ICAs. Error points were found in six vessels. Four WSS spatial distribution patterns were classified according to the location of low WSS values. Reverse WSS was found in 20 vessels. The mean oscillatory shear index (OSI) for these vessels was 0.089 +/- 0.094 (range 1.00 x 10(-6) to 0.490). Complex flow status including reverse velocity, flow stagnancy, and high oscillating WSS was displayed in the end systole of this area. Conclusion: Flow patterns were variant and complicated at the origin of the ICAs. Different types of local WSS spatial distributions were found around the vessel circumference.