AbstractButadiene polymerization in the presence of mixed vanadium–titanium–aluminum catalytic systems containing various organoaluminum compounds (OACs) was investigated. The main factors influencing the activity and stereospecificity of the [VOCl3–TiCl4–OAC1]–(heating)–OAC2 catalysts [where OAC1 and OAC2 were Al(i‐Bu)3, Al(i‐Bu)2H, or Al(i‐Bu)2Cl] were considered. The kinetic parameters of the process were determined. The high activity and stereospecificity of the multicomponent systems probably accounted for the formation of polymerization active sites with both transition‐metal derivatives in their structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 211–217, 2004