To improve the wound-healing ability of chitosan, heparin, known to be effective in wound healing, was complexed with water-soluble chitosan (WSC) by chemical reaction. The chemical structure of the water-soluble chitosan-heparin (CH) complex was analyzed, and CH complex formation was confirmed with an FTIR spectrometer. The mechanical and thermal properties of the CH complex were measured by a tensile tester and thermal analyzers (DSC and TGA). Within the heparin content up to approximate to470 IU/g in the aqueous CH complex solution, the intrinsic viscosity and tensile strength of the water-soluble CH complex gradually increased, but thermal stability slightly decreased by introducing the heparin into the WSC. When the heparin content was greater than these values (470 IU/g), the water-insoluble CH complex, which is supposed to have a multisubstituted or crosslinked structure, precipitated in the aqueous water-soluble CH complex solution. (C) 2003 Wiley Periodicals, Inc.