Metallocenes and other transition metal compounds comprise a new generation of single site catalysts for the production of precisely designed polyolefins and engineering plastics. The discovery of metallocene methylalumoxane (MAO) catalysts has opened a frontier in the area of polymer synthesis and processing. A great number of symmetric and chiral zirconocenes have been synthesized to give isotactic, syndiotactic, isoblock, or stereoblock polymers with increased impact strength and toughness, better melt characteristics or elasticity, and improved clarity in films. Cycloolefin copolymers (COC) and syndiotactic polystyrene can be produced by metallocene catalysts. These are new types of polymers with special properties and a high potential as engineering plastics. Norbornene-ethene copolymers are most interesting for technical uses because of the easily available monomers. Due to different incorporation values of the cyclic olefin in the copolymer, the glass transition temperature can vary over a wide range and reaches 180 ℃. Metallocenes and other transition metal compounds include a new generation of single site catalysts for the production of precisely designed polyolefins and engineering plastics. The discovery of metallocene methylalumoxane (MAO) catalysts has opened a frontier in the area of ​​polymer synthesis and processing. A great number of symmetric and chiral zirconocenes have been synthesized to give isotactic, syndiotactic, isoblock, or stereoblock polymers with increased impact strength and toughness, better melt characteristics or elasticity, and improved clarity in films. Cycloolefin copolymers (COC) and syndiotactic polystyrene can be produced by Metallocene catalysts. These are new types of polymers with special properties and a high potential as engineering plastics. Norbornene-ethene copolymers are most interesting for technical uses because of the easily available monomers. the glass transition temperature can vary over a wide range and reaches 180 ℃.