The pullulans grafted with poly(ethylene glycol) with different degrees of substitution (DS: 0.02-0.2) are synthesized by reaction of pullulan and poly(ethylene glycol) terminated with carboxylic acid. The structure of the resulting modified pullulans is characterized with H-1-NMR and FTIR spectra. The DS of the products increase with the amount of the poly(ethylene glycol) added. The appearances of the products change considerably and the solubility in organic solvent is enhanced visibly. It was found that pullulan derivative is biodegradable. (C) 2003 Wiley Periodicals, Inc.