This chapter discusses the metathesis polymerization of substituted acetylenes. Monomers, polymerization catalysts, controlled polymerizations, polymers, and polymer properties are also discussed in the chapter. Recently, many examples of catalysts for living polymerization of substituted acetylenes have been reported. These catalysts are useful for the elucidation of the polymerization mechanism as well as precision synthesis of various polymer architectures such as block copolymers and star polymers. It is generally difficult to synthesize disubstituted acetylene polymers having protic and/or highly polar substituents such as hydroxy, carboxy, and sulfonic acid groups. Therefore, polymer reactions have been employed to introduce polar groups, and examples of such polymer reactions. Generally, disubstituted acetylene polymers are usually more stable in air, less conjugated, and more lightly colored, and they have stiffer polymer chains than monosubstituted acetylene polymers.