Recent development of olefin polymerization catalysts has caused marked changes in both industrial and academic research. Industrial use of homogeneous metallocene catalysts has already begun in the fields of high density polyethylene and syndiotactic polypropylene. Moreover, important data have been obtained from academic investigations which have proved useful for understanding conventional heterogeneous Ziegler-Natta catalysts. From the industrial viewpoint, however, heterogeneous high-yield catalysts seem to be more important. The present volume contains invited lectures and contributed papers. The following topics are covered: (1) Heterogeneous Catalysts, (2) Metallocene Catalysts and (3) New Trends in the Polyolefin Industry.