This chapter contains sections titled: Introduction Catecholamine Metabolism Proteinase Amino Acid and Peptide Metabolism Polyamine Metabolism Heme Metabolism Carbohydrate Metabolism Steroid Metabolism Purine Metabolism Oxygenations Pterin Metabolism Lipid Metabolism Modification of Proteins and Peptides Vitamin Metabolism Xenobiotic Metabolism Pyrimidine Metabolism Metabolism of Complex Saccharides and Glycoproteins Miscellaneous Nucleic Acid Modification and Expression Summary and Conclusions