Effects of the addition of PDLA oil the crystallization behavior PLLA was investigated by means of differential scanning calorimetry, wide-angle X-ray diffraction, melt rheology, and polarized optical microscopy. Nonisothermal and isothermal crystallization behavior PLLA including low (l-PDLA) and high molecular weight PDLA (h-PDLA) were studied. PLLA/PDLA asymmetric blends form stereocomplex (SC) crystal and stay unmelted at 200 degrees C in the PLLA melt. Nonisothermal crystallization measurement from 200 degrees C showed monotonous rise in the crystallization temperature for PLLA/h-PDLA blend, while peculiar concentration dependence was observed for PLLA/l-PDLA blends. The acceleration effect was more pronounced in PLLA/h-PDLA. although the crystallinity of SC was lower than PLLA/l-PDLA. A blends, which implies the importance of higher order structure of SC for the crystallization of PLLA. From isothermal crystallization kinetics measurements, the acceleration effect in PLLA/h- and l-PDLA blends was found to enhance the nucleation of crystallization but slightly interrupts the crystallization growth. The above results were reasonably explained by the model where SC crystallites are not isolated in PLLA melt but connected like a physical gel.