Homo- and copolymerization of butadiene and styrene in the presence of the catalyst system Nd(octanoate)(3)/CCl4/Al(iBu)(3) (iBu:isobutyl) were investigated at 60 degrees C in heptane as solvent. The initiating catalyst system is very effective in the polymerization of butadiene. However, the presented copolymerization of butadiene and styrene is only practicable when using a special addition order of the catalyst components and a prescribed ageing phase. Copolymers obtained from various monomer feed ratios were characterized by H-1 and C-13 NMR spectroscopy and gel-permeation chromatography (GPC). The copolymer characteristics especially microstructure, molar mass and molar-mass distribution (MMD) are strongly dependent on the composition of the monomer mixture.