Blends of poly(trimethylene terephthalate) (PTT) and poly(buthylene terephthalate) (PBT) in the amorphous state were miscible in all of the blend compositioins studied, as evidenced by a single, composition-dependent glass-transition temperature observed for each blend composition. The variation in the glass-transition temperature was well-predicted by the Gordon- Taylor equation, with the fitting parameter being 1.37. The cold-crystallization (peak) temperature increased with increasing PBT content in the blends. The subsequent melting endotherms after melt crystallization exhibited melting point depression behavior in which the observed melting temperatures decreased with an increasing amount of minor component of the blends. LHW and NLHW were used to determine the equilibrium melting temperature of the blends. The values of the overall crystallization rate parameters for these blends were all found to increase with decreasing crystallization temperature, suggesting that these blends crystallized at low temperatures faster than that at high temperatures. As the content of PBT was further increased, these values dramatically decreased. This result is similar to that observed in the growth rate. From LH secondary nucleation theory, PTT ,PBT and their blends showed the transition temperatures between regime III and II about 194oC. Banded spherulites were observed for PTT/PBT blends. The spacing of bands of PTT increases with increasing Tc. The body of spherulite texture is more open with increasing PBT content. In addition, the boundary of spherulite is also changed with composition.