2,2-Dibutyl-2-stanna-1,3-dioxepane (DSDOP) was polycondensed at 80 degrees C in bulk with succinyl chloride, adipoyl chloride, suberoyl chloride, sebacoyl chloride, and 1,12-dodecanedioyl chloride. In the case of adipoyl chloride the stoichiometry was varied and the temperature in the case of sebacoyl chloride. With a slight excess of the dicarboxylic acid chlorides, macrocyclic polyesters were obtained as the main reaction products in all cases. Depending on the dicarboxylic acid dichloride the ratio of polycondensation/cyclization steps was of the order of 20/1 to 100/1. The temperature had little influence provided that the reaction mixture remained liquid and homogeneous over the whole course of the polycondensation. Macrocyclic polyesters were also obtained as the main products when the noncyclic 1,3-bis(tributylstannoxy)butane was used as monomer. It is demonstrated that the cyclic oligo- and polyesters are not the result of transesterification and backbiting degradation processes.