Abstract-Hydroboration of terminal and internal alkenes with pinacolborane (1.2 equivalents) was carried out at room temperature in the presence of an iridium(I) catalyst (3 mol%). Addition of dppm (2 equivalents) to [Ir(cod)Cl] 2 gave the best catalyst for hydroboration of aliphatic terminal and internal alkenes at room temperature, resulting in addition of the boron atom to the terminal carbon of 1-alkenes with more than 99% selectivities. On the other hand, a complex prepared from dppe (2 equivalents) and [Ir(cod)Cl] 2 resulted in the best yields for vinylarenes such as styrene.These complexes exhibited higher levels of catalyst activity and selectivity than those of corresponding rhodium complexes.