I. Vanadium in the Biosphere.- II. The Coordination and Redox Chemistry of Vanadium in Aqueous Solution.- III. The Essentiality and Metabolism of Vanadium.- IV. Vanadates as Phosphate Analogs in Biochemistry.- V. Vanadium Haloperoxidases.- VI. Vanadium Nitrogenases.- VII. Insulin Mimetic Effects of Vanadium.- VIII. Vanadate Sensitized Photocleavage of Proteins.- IX. Vanadium in Ascidians.- X. Biological Applications of 51V NMR Spectroscopy.- XI. Biological Applications of EPR, ENDOR, and ESEEM Spectroscopy.