Polymerization of (o-methylphenyl)acetylene (o-MePA) by MoOCl4-n-Bu(4)Sn-EtOH catalyst in toluene at 0 degrees C provided a cis-rich living polymer; cis 77%, M(W)/M(n) = 1.21. The polymerization at -30 degrees C gave results similar to those for 0 degrees C, whereas the polymer obtained at 30 degrees C exhibited a broader molecular weight distribution (MWD) and a lower cis content. Among several organotin compounds, only n-Bu(4)Sn was effective for the living polymerization of o-MePA. The bulkier the alkyl group of alcohols as the third catalyst component, the broader the MWD of the polymer, while the geometrical structure was not affected by the alcohols.