Cascade-branched, "graft on graft" polybutadienes, denoted arborescent graft polymers, were prepared by hydrosilylation of polybutadiene vinyl groups with chlorodimethylsilane, followed by grafting with living polybutadiene chains. Repeated hydrosilylation-anionic grafting cycles led to a treelike outward growth, yielding well-defined, spherically shaped macromolecules. The molecular weight of the materials increased dramatically with each grafting cycle, since polymer chains rather than small molecules were used as building blocks. The materials were characterized by means of gel permeation chromatography, static light scattering measurements, and viscosimetry.