The effect of amorphous poly(D,L-lactide) (PDLLA) on the molecular orientation and crystallization of crystalline poly(L-lactide) (PLLA) on stretching is reported in this study. It is indicated that the presence of PDLLA in its miscible blends with PLLA is not favorable for either cohesive mesophase formation below Tg or strain-induced crystallization above Tg at strains beyond the segmental extensibility limit. Because of lack of constraints imposed by cohesive mesophase or crystals, oriented segments are liable to slide each other or recoil, responsible for low-molecular orientation in the stretched blends. POLYM. ENG. SCI., 2013. (c) 2012 Society of Plastics Engineers