This volume summarizes knowledge on vitamin C (ascorbic acid), the major water-soluble antioxidant vitamin which was discovered by Albert Szent-Gyrgyi resulting from research work in basic science, epidemiology and clinical medicine. Fundamental molecular, biological and physiological properties of ascorbic acid are presented, and knowledge on the role of vitamin C in major diseases such as cancer is critically evaluated. The aim of the book is to contribute to a better understanding of the potential beneficial use of the compound in disease prevention or treatment.