Manganese**I wish to dedicate this chapter to the memory of the late George C. Cotzias, M.D., a leader in the field of manganese metabolism and extrapyramidal disorders.His genial inspiration and meticulous perseverance at work made collaborating with him a privilege and a continuous lesson.His premature death has deprived this field of medicine of a substantial contributor in the efforts of slaying the common dragon of disease.