AbstractPolydideuteroethylenes having some stereoregulated structure were prepared by polymerizing trans‐ and cis‐1,2‐dideuteroethylene using a Ziegler catalyst. trans and cis‐dideuteroethylene were prepared by reducing dideuteroacetylene with chromous chloride solution and copper activated zinc dust, respectively. Infrared spectra of the two polymers obtained showed significant differences particularly in the bending vibration bands of CHD groups. Bands at 1335 and 1288 cm.‐1 were observed only in polymers of the trans isomer, and a band at 1305 cm.‐1 was observed only in polymers of the cis isomer. Densities, melting points, intrinsic viscosities, and crystallinities of the polymers were measured and compared with those of normal polyethylene. The x‐ray diffraction patterns of the polydideuteroethylenes were almost identical with that of normal polyethylene.