A composite chitosan-cellulose membrane was prepared by coating chitosan on filter paper. Physical properties of the composite membrane and its application in affinity membrane immunoadsorption (IgG to immobilized Protein A) were examined. The chitosan and porogen (polyethylene glycerol, PEG) contents in the chitosan preparation solution have a significant effect on porosity of the membrane and the flow rate of water through the membrane. The effect of the evaporation time (ET) of the solution after coating on the flow rate was also determined. The composite membrane with a relatively large flux (3.2 ml/min/cm(2) at 12.5 psi) and approximately 1 mum pore size was prepared by using a 0.5% chitosan solution containing 15.0% PEG and evaporating the solution for 3 h at room temperature after coating. The obtained composite membrane provided tensile strength larger than the plain cellulose support, in both wet and dry states. The hydroxyl groups on the composite membrane were modified with an 11-atom spacer arm to link Protein A as an affinity ligand. For comparison, the plain filter paper was also linked with Protein A using the same method. The amount of Protein A immobilized was 1.36 and 6.29 mg/ml membrane on the plain filter paper and the composite membrane, respectively. The composite membrane provided a relatively high dynamic binding capacity of human IgG at 14.9 mg/ml membrane, which is four-fold higher than that of the plain filter paper.