Calcium bilirubinate (CaBR) particles were synthesized in three systems, such as pure water, glucan and polyethylene glycol (PEG) aqueous solutions, respectively. The polymorph and morphology of the particles were investigated using Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM) and X-ray diffraction spectroscopy (XRD). The results revealed that the CaBR formed in pure water was amorphic and quasi-spherical with a mean diameter of about 80 nm. The glucan in solutions made the size of spheric CaBR particles increased obviously, but the crystallinity of particles was not improved apparently. The oriented growth of fusiform CaBR crystals was induced by PEG successfully. The average length of the crystals was 170 nm and the diameter 26 mn. The formation mechanism of CaBR crystal controlled by PEG was also discussed in this article. (c) 2006 Elsevier Ltd. All rights reserved.