Polymerization of phenylacetylene (PA) with [(cod)IrCl](2)-based catalysts (cod: 1,5-cyclooctadiene) was examined. The [(cod)IrCl](2)/n-BuLi and [(cod)IrCl](2)/ Ph2C=C(Ph)Li systems induced the polymerization of PA to produce polymers with a number-average molecular weight (M-n) of around several thousand in rather low yields. On the other hand, the catalyst composed of [(cod)IrCl](2), norbornadiene (nbd), Ph3P, and Ph2C=C(Ph)Li (molar ratio of 1:1:1.1:2) produced polymer in a high yield (ca. 80%) in toluene at 0 degreesC. The resulting polymer showed a bimodal gel permeation chromatographic profile (M-n = 209,000 and 4300; ratio: 81/19). On the basis of these findings, the presence of two active species, that is, Ir complexes with nbd,and cod, are discussed.