Organometallic complexes of iridium have gained importance because of their novelty, reactivity and applications in diverse fields. In this book, the authors present current research in the study of the occurrence, characteristics and applications of iridium. Topics include the synthetic methods of different classes of volatile organometallic and co-ordination compounds of iridium; homogeneous iridium catalysts in aqueous solution; applications of iridium catalysts in green chemistry; iridium-carbonyl complexes of nitrogen-oxygen and phosphorous-oxygen donor ligands; iridium-catalysed allylic substitutions; a novel amperometric transducer electrode with iridium-niobium binary alloys; and highly efficient electrophosphorescent organic light-emitting diodes based on iridium (III) complexes containing carbazole units.