Computer-aided design (CAD) plays a key role in a variety of medical applications including prosthesis design, surgical implant design, blood flow analysis, preoperative planning for surgical operations, and computer-assisted surgery. CAD tools and technology developed for mechanical design have been successfully applied to geometric modeling, visualizing, animating, and analyzing the natural functional behavior of anatomical structures including human skeletal and vascular systems. These shape modeling and visualization tools provide a significant amount of design information concerning object shape, dimensional parameters, component materials, material flow, and interference checking. New developments in virtual reality (VR) and rapid prototyping (RP) technologies have also enabled biomedical engineers to create detailed three-dimensional (3-D) models of anatomical structures directly from the CAD database. The immersive VR environments provide designers, physicians, and surgeons with the ability to interactively manipulate the geometric CAD models with 3-D displays and haptic devices. In contrast, the fabricated RP prototypes give surgeons a realistic hard copy of complex structures before a medical implant is inserted or a surgical procedure is performed. The shift from the purely graphical interpretation of complex geometric models displayed on a computer monitor to an interactive visual-tactile representation of the anatomical structure has the ability to deliver a new level of spatial understanding to designers and medical personnel.