The broadening practical use of chlorosulfonated polyethylene elastomers for applications where good resistance to heat, oil, light, oxygen, and ozone is needed has been accelerated by the development of several chemically distinct curing systems. Optimum use of these saturated elastomers requires a knowledge of the chemistry of these curing reactions and the effect of the resulting crosslink structures on vulcanizate properties. The high reactivity of the sulfonyl chloride crosslinking sites allows wide latitude in choice of curing chemistry, and crosslink type can be controlled to give a preponderance of ionic salt bonds or to give a mixture of covalent and ionic bonds. The role of water, alcohols, sulfur accelerators and free radical stabilizers in the various practical curing systems is discussed. The development of wholly organic curing systems for chlorosulfonated polyethylenes is reviewed. The properties of vulcanizates of chlorosulfonated polyethylenes are also significantly controlled by the base polyethylene, by chlorine content, and by chlorine distribution. The effects of these variables on vulcanizate properties is briefly reviewed.