The effect of alpha-cyclodextrin (alpha-CD) on the crystallization behavior of poly(3-hydroxybutyrate) (PHB) was investigated with polarized optical microscopy, differential scanning calorimetry, and wide-angle X-ray diffraction. We found that the addition of alpha-CD can greatly accelerate the crystallization of PHB and that alpha-CD has a potential not only to enhance the nucleation but also to accelerate the crystallization of PHB. Compared to a conventional nucleation agent, such as talc, alpha-CD is a natural product and has many advantages because it is environmentally friendly and safe to humans. (C) 2004 Wiley Periodicals, Inc.