Butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene and 4-methyl-1,3-pentadiene have been polymerized with MAO/Cp’VCl2 . 2PEt(3) and MAO/Cp(2)VCl (Cp’=C(5)H(4)Me, Cp=C5H5). Polymers, predominantly cis-1,4, have been obtained from butadiene and pentadiene, a polymer with a mixed cis/trans structure has been obtained from 2-methyl-1,3-pentadiene, while 4-methyl-1,3-pentadiene gave a predominantly 1,2 polymer. Cp’VCl2 . 2PEt(3)/MAO was found to be particularly active. The different stereospecificities of the systems are discussed with respect to other soluble vanadium systems.