To investigate the effect of orientation and orientation mode on crystallization rate, crystallization and melting behaviors of oriented amorphous poly(ethylene terephthalate) (PET) fibers and films were analyzed using the fast scanning chip calorimetry (FSC) and the conventional differential scanning calorimetry (DSC). Uni-axially oriented fibers with various degrees of molecular orientation were prepared through the melt-spinning with various take-up velocities and bi-axially oriented films were prepared through the simultaneous equi-biaxial stretching of amorphous and isotropic PET films to various draw ratios at 90 degrees C. In the FSC measurement, significant data fluctuation caused by the thermal shrinkage of the oriented sample was observed at around the glass transition temperature (Tg). We found that this fluctuation could be suppressed without a considerable effect on crystallization behavior by applying preliminary shrinkage process which contains heating up to 120 degrees C and immediately cooling down to a temperature blow Tg at high heating and cooling rates. Based on this technique, measurement of the cold crystallization behaviors was conducted at various heating rates applying the time-temperature profiles including the pre-thermal treatment. The models for crystallization kinetics proposed by Ozawa1) and Nakamura2) were combined to calculate the non-isothermal crystallization rate of oriented PET fibers and films. Even after applying the thermal shrinkage, the highly oriented fibers or films showed much faster crystallization rate than that for the barely oriented fibers or isotropic films. 1) T. Ozawa, Polymer, 12, 150 (1971) 2) K. Nakamura, K. Katayama, T. Amano, J. Appl. Polym. Sci., 17, 1031 (1973)