The role of transition metals in biological systems is an area 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 in 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.