The development and use of medical and dental materials are highly interdisciplinary endeavors which require expertise in chemistry, materials science, medicine and/or dentistry, mechanics and design engineering. The Symposium upon which this treatise is based was organized to bring members from these communities together to explore problems of mutual interest. The biomaterials which are used in medical or dental prostheses must not only exhibit structural stability and provide the desired function, but they must also perform over extended periods of time in the environment of the body. The latter is a very stringent requirement. The oral and other physiological environments are designed by nature to break down many organic substances. Also of importance is the requirement that materials used in the prosthesis not have a deleterious effect on body tissues. Most foreign (to the body) substances are somewhat toxic to human tissues; in fact, few factors are more limiting in the medical prosthesis field than the biocompatibility problem. Some of these problems and the attempts to solve them are discussed in this volume.