Thrombosis and thromboembolism still plague cardiovascular prosthetic devices. While it is known that areas of stasis and stagnation will result in thrombus formation, the potential for embolization remains unknown. The local fluid dynamics, in particular, the local shear stress, play an integral role with embolization. A backward facing step model was used to investigate thrombus formation and embolization. Through the use of an in vitro blood loop with radiolabeled platelets, high and low Reynolds number flows were investigated. In addition, computational fluid dynamics (CFD) simulations under the same conditions and the same model dimensions were executed with an added simulation involving a clot formed beyond the step to understand how clot growth affects the local flow. The results indicate that areas of high Reynolds number flow produce substantial thrombus with both techniques. The low Reynolds number flow with the blood loop showed no visible thrombus, but the simulations illustrated a recirculation zone suggesting potential for thrombus formation. The simulated CFD clot formation showed a change in the local flow with an increase in shear stress suggesting embolization might occur. Further refinement in the CFD and more blood studies at higher Reynolds number are required to induce embolization. This work is an initial step towards understanding how thromboembolization and the local fluid dynamics are related.