Abstract: The biological roles of vitamin C (ascobic acid) are discussed for nutritionists, physicians, and health and disease researchers. Attention is specifically given to vitamin C metabolism; estimating body reserves of vitamin C; the roles of vitamin C (e.g., as a reducing agent); factors affecting vitamin C reserves and requirements; therapeutic aspects; and safety considerations concerning high vitamin C intake. The synthesis of vitamin C is outlined; details of the breakdown of vitamin C remain unknown. A number of unresolved and often controversial areas are examined in detail. Intake and body reserve levels of vitamin C are suggested which should be appropriate for maintaining health and combating disease. (wz).