A novel WOCl4-based ternary catalyst, WOCl4-n-Bu4Sn-t-BuOH, induced the living polymerization of [o-(trifluoromethyl)phenyl] acetylene. A catalyst composition of WOCl4-n-Bu4Sn-t-BuOH = 1:1:1 was suitable, and sterically crowded alcohols such as t-BuOH were favorable as the third catalyst components. The polydispersity ratio of the polymer formed in anisole at 30 degrees C was as small as 1.04, and the initiation efficiency was no more than about 2%. The living nature of the polymerization was confirmed by the dependence of polymer molecular weight on conversion. Further, two WOCl4-based binary systems, WOCl4-n-BuLi (1:1-2) and WOCl4-EtMgBr (1:1), were also useful as living polymerization catalysts. The polydispersity ratio and the initiation efficiency for the former system (W:Li = 1:1) were 1.08 and 0.9%, respectively, and those for the latter were 1.11 and 5%. These are the first examples of W-based catalysts effective for the living polymerization of substituted acetylenes.