Long chain branching (LCB) can be introduced into EPDM during polymerization by several mechanisms.  These include cationic coupling through unsaturation in the polymer chain initiated by Lewis acids, polymerization through both double bonds in the diolefins and re-incorporation of macromers through unsaturation at the chain end.  These branching mechanisms are reviewed, with particular emphasis on branching by polymerization and its propensity for gellation.  The development of VNB EPDM free from macro-gel formation through novel control of this branching mechanism is highlighted.  LCB characterization methods and impact of LCB on polymer attributes is also discussed.