As-spun poly(trimethylene terephthalate) (PTT)/poly(ethylene terephthalate) (PET) side-by-side conjugate fibers were drawn to investigate the effects of drawing conditions on structure development and physical properties. Effects of draw ratio and heat-set temperature were observed. In the state of an as-spun fiber, the molecular orientation of PTT was higher than PET, whereas PET molecular orientation increased remarkably over PTT with increasing draw ratio. Crimp contraction increased sharply at a draw ratio over 2.0, where the crystalline structure of the PET developed sufficiently. A heat-set temperature of at least 140 degrees C was required to develop sufficient crimp contraction. The crystallinity and orientation of the PET were attributed mainly to the crimp contraction of the drawn fiber. POLYM. ENG. SCI., 51:232 236, 2011. (C) 2010 Society of Plastics Engineers