The macroscopic and microscopic melt-crystallization kinetics of poly(trimethylene terphthalate) (PTT)/polycarbonate (PC) blends have been measured by differential scanning calorimetry (DSC), and optical microscopy (OM). The results are analyzed in terms of the Avrami equation and the Hoffman-Lauritzen crystallization theory (HL model). Blending with PC did not change the crystallization mechanism of PTT, but reduced the crystallization rate compared with that of neat PTT at the same crystallization temperature. The crystallization rate decreased with increasing crystallization temperature. The spherulitic morphology of PTT was influenced apparently by the crystallization temperature and by the addition of PC. X-ray diffraction shows no change in the unit cell dimension of PTT was observed after blending. Through the HL theory, the classical regime II -> III transition was detected for the neat PTT and the blends. The nucleation parameter (K-g), the fold-surface free energy (sigma e), and the work of chain folding (q) were calculated. Blending with PC decreased all the aforementioned parameters compared with those of neat PIT. POLYM. ENG. SCI., 50:1036-1046, 2010. (C) 2010 Society of Plastics Engineers