Biological nitrogen fixation provides more than 50% of the total annual input of the essential element nitrogen to world agriculture. Thus, it is of immense agronomic importance and critical to food supplies, particularly in developing countries.

1. Nitrogen Fixation: An Historical Perspective.- 2. Haber-Bosch and Other Industrial Processes.- 3. Assay Methods for Products of Nitrogenase Action on Substrates.- Chanter 4. The Structures of the Nitrogenase Proteins and Stabilized Complexes.- Chanter 5. The Mechanism of Mo-dependent Nitrogenase: Thermodynamics and Kinetics.- 6. Strategies for the Functional Analysis of the Azotobacter Vinelandii MoFe Protein and its Active Site FeMo-Cofactor.- 7. Chemical Models, Throretical Calculations, and Reactivity of Isolated Iron-Molybdenum Cofactor.- Chanter 8. Structural Models for the FeMo-cofactor and the P Clusters.- 9. Biosynthesis of Iron-Molybdenum and Iron-Vanadium Cofactors of the nif- and vnf-encoded Nitrogenases.- 10. Vanadium Nitrogenase.- 11. Iron-only Nitrogenase: Exceptional Catalytic, Structural and Spectroscopic Features.- 12. Superoxide-dependent Nitrogenase.- Chanter 13. Future Challenges and Prospects.- Subject Inde.