The effect of branching on the crystallization behavior of poly(ethylene terephthalate) has been examined by nonisothermal crystallization studies, using DSC. It was found that branching causes a significant change in the crystallization behavior, in that the Avrami exponent n lies between 1 and 2, suggesting a rodlike growth process compared to a spherulitic one observed in the case of PET. In addition, the effect of molecular kinks and linear disruptions were also examined; in both these cases, however, the same spherulitic growth, as seen in the case of PET, is observed. Further, the presence of branching, kinks and linear disruptions, in small concentrations, appears to enhance the crystallization process, possibly, by acting to facilitate nucleation. At higher concentrations of such defects, however, the crystallization process is slowed down and the overall crystallinity of the PET copolymers is reduced.