THE in vivo corrosion environment is complex, characterized by dynamic, constantly changing chemical and physiological processes, mechanical loading patterns, and bioelectric potentials. There is, in fact, more than one in vivo environment. Subenvironments, each presenting rather discrete corrosion conditions, exist, e.g., the oral cavity, the cardiovascular system, the environment surrounding orthopaedic implants, etc. Implant materials are vulnerable to various forms of corrosion attack. For some materials under certain conditions, uniform attack, pitting, crevice corrosion, galvanic corrosion, and various forms of interaction between applied loads and corrosion (fretting, corrosive wear, corrosion fatigue, and stress-corrosion cracking) have been reported.