New hydrogenated ring-opening metathesis polymers with excellent thermal and optical properties were developed. These polymers were prepared by the ring-opening metathesis polymerization of ester-substituted tetracyclododecene monomers followed by the hydrogenation of the main-chain double bond. The degree of hydrogenation was an important factor for the thermal stability of the polymers, and as complete hydrogenation as possible was necessary to obtain a thermally stable polymer. The completely hydrogenated ring-opening polymer derived from 8-methyl-8-methoxy-carbonyl-substituted monomer has a glass-transition temperature of 171 degreesC and a 5% weight-loss temperature of 446 degreesC. This polymer has excellent thermal and optical properties because of its bulky and unsymmetrical polycyclic structure in the main chain and is an alternative to glass or other transparent polymers such as poly(methyl methacrylate) and polycarbonate resin. This polymer has also been used in a wide variety of applications, such as optical lenses, optical disks, optical films, and optical fiber.