This paper discusses the competing chemical reactions involved in the peroxide vulcanization of elastomers. Each of these reactions can have a profound effect on the cure characteristics as well as on the properties of the final vulcanizate. The balance between these reactions is determined by several factors including the type of polymer, type and concentration of peroxide, cure temperature, and the presence of other compound additives such as co-agents and antidegradants. The effects of all of these factors are discussed.