New linear polyesters containing sulfur in the main chain were obtained by melt polycondensation of diphenylmethane-4,4＇-bis( methylthioacetic acid) (DBMTAA) or diphenylmethane-4,4＇-bis(methylthiopropionic acid) (DBMTPA) and diphenylmethane-4,4＇-bis(methylthioethanol) (DBMTE) at equimolar ratio of reagents (polyesters E-A and E-P) as well as at 0.15 molar excess of diol (polyesters E-A(OH) and E-P-OH). The kinetics of these reactions was studied at 150, 160, and 170 degrees C. Reaction rate constants (k(2)) and activation parameters (Delta G(not equal), Delta H-not equal, Delta S-not equal) from carboxyl group loss were determined using classical kinetic methods. E-A and E-P ((M) over bar(n) = 4400, 4600) were used for synthesis of new rubber-like polyester-sulfur compositions, by heating with elemental sulfur, whereas oligoesterols E-A(OH) and E-P-OH ((M) over bar(n) = 2500, 2900) were converted to thermoplastic polyurethane elastomers by reaction with hexamethylene diisocyanate (HDI) or methylene bis(4-phenyl isocyanate) (MDI). The structure of the polymers was determined by elemental analysis, FT-IR and liquid or solid-state H-1-, C-13-NMR spectroscopy, and X-ray diffraction analysis. Thermal properties were measured by DTA, TGA, and DSC. Hardness and tensile properties of polyurethanes and polyester-sulfur compositions were also determined.