This review deals with currently employed methods for the synthesis of phosphate monoesters and phosphoramidates of biological molecules. The phosphorylating agents discussed are phosphoric acid, its esters and anhydride, the phosphorochloridates and -chloridites, and phosphites. Specific applications to nucleic acid, carbohydrate, protein, lipid, coenzyme, and steroid chemistry are discussed. 1. Introduction 2. 5- and 6-Membered Cyclic Phosphorylating Agents 3. Phosphoric Acid and Phosphoric Acid Anhydrides 4. Phosphoric Acid Monoesters 5. Phosphoric Acid Diesters 6. Phosphoric Acid Triesters 7. Phosphoryl Chloride 8. Phosphorochloridates 9. Phosphorodichloridates 10. Phosphites and Phosphorochloridites 11. Miscellaneous Reagents