The processing properties are strongly influenced by the molecular structure especially in extension dominated processing operations. A way of improving the extensibility of polymer melts is the introduction of long-chain branches, which can be achieved by different methods. This book deals with the correlations between the synthesis conditions and the molecular structure of metallocene catalyzed polyethylenes and its ethene-/ α‑olefin copolymers. The new class of the metallocene catalysts is able to produce materials with a very well controlled molecular architecture. The structure analysis is primarily carried out with SEC-MALLS and shear rheology. Several correlations between the molecular structure and the rheological properties are described as well as connections to the synthesis conditions.