The occurrence of tin in plants, animals and humans is discussed, in relation to its abundance in the lithosphere and hydrosphere and the range of the different tin(II) and tin(IV) complexes formed. A reasoned consideration of its essentiality for living species is provided. It is concluded that tin is beneficial, even if not yet proved to be an essential element. After reference to the chemistry of tin compounds, there is a detailed discussion of their toxicity in animals and humans. Feasible routes for tin intake and uptake into humans are described. The past and current use of tin pharmaceuticals is reviewed and the areas for which they are currently permitted for use in humans as dentifrices and mouth washes, as radio-pharmaceuticals and for the treatment of jaundiced newborns are described. A detailed review of tin-containing antitumour agents as representative tin pharmaceuticals is also given. Finally, a list of tin-containing drugs and drug candidates is also shown.