The products of Ziegler-Natta catalyzed reactions, including high density polyethylene, polypropylene, and other thermoplastics and elastomers, have become familiar to all. While an enormous volume of experimental work was completed during the 1950s and 1960s, it has only been during the 1970s that the multiplicity of mechanistic schemes developed have been subjected to scrutiny. The majority of these have been concerned with polymerization of ethylene and α-olefins and because they have been adequately reviewed recently, are discussed only briefly here. A similarly large volume of empirical experimental work has enabled commercial production of polybutadiene using stereoregular catalysts. However, the mechanisms involved are of recent development, largely due to the additional configurational complexity of products, the multicompound nature of the catalyst complex, and the susceptibility of the system to contamination. Advances which have been made during the last decade are highlighted, with particular emphasis on those modifications to catalyst or to polymer structure which are of practical importance. In Australia, all production of stereoregular (high cis) polybutadiene is achieved using an aluminum alkyl halide-cobalt salt based catalyst. The fundamental technology of this process is discussed with emphasis upon process control. In particular, the control of molecular weight, processing behavior, and reduction in cross-linked material are included in more recent developments. In a broader context, technological changes which have been stimulated by such diverse influences as the increased awareness of industrial hygiene, fluctuations in feedstock availability and cost, and the general acceptance of radial ply tires are discussed. Experimental activities currently in progress in Australia, together with challenges still remaining, are examined.