This book elaborates on the theme of dehydrogenases. It considers dehydrogenases as enzymes with distinct functions in the cells with the help of various substrates, like aldehyde dehydrogenases, pyruvate dehydrogenase complex, succinate dehydrogenase, hydroxysteroid dehydrogenases, glucose-6-phosphate dehydrogenase, and glutamate dehydrogenase. They are evaluated from various viewpoints like physiological functions, biochemistry, and role in few diseases as well as in the development of tumors. The book encompasses several topics organized under sections such as dehydrogenases and cancer; dehydrogenases and some other diseases; and its physiological role. It will serve as an important source of reference to those interested in the field.