It is a challenge to write a textbook on intermediate metabolism at present, as the field is in a state of constant flux, with new significant findings being reported daily. The ability to work with isotopes, the refinement of analytical methods, and the localization of metabolic processes at the morphological elements of the cell have provided powerful impulses to metabolic research. Despite all the difficulties, I have decided to write a textbook on intermediate metabolism primarily because there is no recent monograph on this topic in the German-speaking world, which not only disrupts teaching but also makes it extremely difficult for many researchers dealing with medical and biological questions.