Bromobutyl (BIIR) is an isobutylene–isoprene copolymer containing reactive bromine. Because bromobutyl has the predominately saturated polyisobutylene backbone of butyl rubber, it has many of the attributes of the butyl polymer molecule. These attributes include its mechanical properties, vibration dampening, low permeability, and resistance to aging and weathering from environmental exposure. The modern radial tire was in many respects made possible through the introduction and use of bromobutyl rubber innerliners. Use of this polymer in the tire innerliner compound has allowed improvements in air retention, oxygen permeation, liner-to-tire casing adhesion, and tire durability. This paper on the formulation and properties of tire bromobutyl innerliner compounds also wishes to provide fundamental information on polymer system selection needed to ensure the bromobutyl compound will meet required processing and final mechanical properties. This will help ensure the tire or industrial products using these polymers meet durability and performance parameters that are required in the final end product.