Transition metal-catalyzed cycloaddition reaction of unsaturated substances, such as alkynes and alkenes, is one of the most important methods for the synthesis of mono-ring and multi-ring systems. In this paper, the recent progress in iridium-catalyzed cycloaddition reactions is reviewed, mainly including [2＋ 2＋1], [2＋2＋2], [4＋2], 1,3-dipolar cycloaddition reactions. In addition, some iridium-catalyzed [3＋2＋2], [3＋2] and [5＋1] cycloaddition reactions are described. Some parts of cycloaddition reaction mechanisms are also discussed.

Key words: iridium catalysis, cycloaddition, iridium complex