A wide variety of polyesters and polyamides was prepared from 1,2- and 1,3-disubstituted cyclobutane derivatives. In general, polyamides containing the trans-disubstituted cyclobutane ring were crystalline. Polyesters containing predominantly the trans-isomer tended to be crystalline but those containing mixtures of cis-trans isomers were amorphous. Mechanical properties have been determined wherever possible. Appreciable yields of cyclic dimers were isolated during the preparation of certain polyesters. These cyclic dimers readily polymerized when treated with dibutylzinc. Examination of acrylonitrile dimer (1,2-dicyanocyclobutane) by gas chromatography failed to reveal the presence of any 1,3-dicyanocyclobutanes.