New examples for the monomer-isomerization polymerizations of some branched internal olefins, 4-methyl-2-pentene and 4-phenyl-2-butene, are presented. When these olefins are polymerized with A1(C2H5)3-TiCl3([TiCl3] = 120 mmole/liter, A1/Ti = 3.0) catalyst at 80°C, considerable amounts of high polymers [27.5%/60 hr ([η] = 0.68 d1/g) and 35.6%/100hr, respectively] were obtained. From the additional fact that the isomerization from these 2-olefins to the mixture of their positional isomers including 1-olefins was observed during the polymerization, it is assumed that the polymerizations from these 2-olefins are performed with the 1-olefins which isomerized from the starting 2-olefins.