The polymerization of aliphatic disubstituted acetylenes was examined with MoOCl4-n-Bu4Sn-EtOH (1/1/2) ternary catalyst in anisole at 0 degrees C. Various linear aliphatic disubstituted acetylenes such as 2-nonyne provided polymers with narrow molecular weight distributions (weight-average molecular weight/number-average molecular weight = 1.05-1.20). The living character of the polymerization was proven by bath the time profile of the polymerization and the multistage polymerization of 2-nonyne. The initiation efficiency was about 3%, which is rather low. Although 5-do-decyne, which has a triple bond in a more inner part, polymerized more slowly than 2-nonyne, their living characters were hardly different. Diblock copolymers were synthesized by the sequential living polymerization of internal linear alkynes.