The change of crimp contraction and shrinkage in the melt spinning and drawing process of polyethylene terephthalate (PET) side-by-side bicomponent fibers was studied. Regular PET and modified PET were selected to make a latent crimp yarn. The modified PET was synthesized to increase thermal shrinkage. The crimp contraction is mainly dependent on drawing conditions such as draw ratio, heat-set temperature, and drawing temperature. Difference in shrinkage between the PET and the modified PET causes the self-crimping of bicomponent fibers. Although changing the heat-set temperature and the drawing temperature can not affect dimensional change, the crimp contraction varies with those variables. As the heat-set temperature and the drawing temperature decrease, the crimp contraction increases. Difference in elongation also affects the crimp contraction in the effect of draw ratio. When the modified PET with neopentyl group was used for highly shrinkable part, the crimp contraction is greater in comparison with modified PET with dimethyl isophthalate. (c) 2006 Wiley Periodicals, Inc.