Molecules of biological interest for in-vivo and in-vitro research or diagnostics of metabolic functions and of neuro-transmission are very often labeled with iodine. Based on state-of-the-art research, this compendium describes the major production routes of the six most relevant iodine radio isotopes and the various methods of labeling molecules of biological, diagnostic or pharmaceutical interest with them. The chapters describe the basic reaction mechanisms, and the influence of iodine introduction on physical/chemical and pharmacological properties. They also include examples of important reaction pathways for the preparation of radio-iodine compounds. The volume is completed by an expert system providing guidelines to obtain the most suitable method of synthesis regarding also cost and time aspects. Worked examples support the novices confronted with radio-iodination reactions.