The role of the transition metals in biological systems is of great interest to chemists: the chemical properties of these metals often define the biological function of the proteins and systems these metals are found in. In this introductory text students are introduced to a number of topics: the transport and storage of metals: their functions is dioxygen interactions, electron transfer, and enzyme activity; the therapeutic uses of coordination compounds: and the role that small-molecule models can play in advancing our knowledge of the structure and function of transition metals contained in metallobiosites.