A living polymerization of ethylphenylketene (EPK) was accomplished. When polymerization of EPK was carried out with butyllithium as an initiator in tetrahydrofuran (THF) at -20 degrees C, EPK was completely consumed within 5 min, and the corresponding polyester with narrow molecular weight distribution (M-w/M-n similar to 1.1) was obtained almost quantitatively. Kinetic study of the polymerization at -78 degrees C revealed that conversion of EPK agreed with the first-order kinetic equation, and that M-n of the polymer increased in virtually direct proportion to the conversion. Along with these results, successful results in postpolymerization at -20 degrees C strongly supported living mechanism of the present polymerization. Further, lithium alkoxides having a methoxy group, styryl moiety, and nitroxyl radical, also successfully initiated polymerization of EPK to afford the corresponding polymers having functional initiating ends. In the polymerization with varying feed ratio [EPK](o)/[initiator](o), the linear relationship between the feed ratio and M-n of the obtained polymer was observed, while maintaining narrow M-w/M-n.