Poly(sebacic acid-octadecanoic diacid) copolyanhydrides (PSAOAs) were prepared by melt polycondensation of sebacic acid (SA) and octadecanoic diacid (OA). PSAOAs were characterized by Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and wide angle X-ray diffraction (XRD). In vitro degradation experiments and SEM micrographs show that the degradation rate of PSAOAs decrease with increasing the content of POA in copolyanhydrides and the erosion process of PSAOAs is neither bulk nor perfect surface erosion but rather has elements of both in phosphate buffer at 37 degrees C. In vitro release experiments and SEM micrographs indicate that the release rate of drug from the drug-loaded PSAOAs discs decreases with increasing the content of POA in copolyanhydrides and the release rate of the hydrophilic drug is greater than that of the hydrophobic one. The results of the investigation suggest that POA can improve the properties of PSA and promote the applications of PSA in biomedicine. (C) 2008 Elsevier Ltd. All rights reserved.