Thromboembolism (TE) significantly limits the usefulness and safety of blood-contacting devices, such as hemodialysis catheters, coronary stents, etc. Computer simulation of TE can provide understanding of the process and can facilitate the design of more effective devices. A computation tool has been developed at BYU by adding quantitative TE code to a commercial computational fluid dynamics (CFD) package (Star-CD). This three-dimensional model, based on a previous two-dimensional model developed at BYU, predicts thrombus initiation and growth and adjusts flow to accommodate thrombus geometries. The 3D tool has been applied to three hemodialysis catheter designs and two stent geometries, and thrombosis has been experimentally assessed in the catheters for comparison. Animations of dynamic thrombus formation in the various geometries will be presented.