Clustering patameters, as well as integral and partial thermodynsmic functions and Huggins parameter of the cellulose amorphous regions - water system have been determined on the basis of sorption and calorimetry data. Clustering has been shown not to proceed in this system. Compatibility of the components has been determined according to the enthalpy and entropy changes in the region of lower water contents. With higher water contents, entropy decreases, and enthalpy absolute value increases; enthalpy contribution to the free energy of the system forming becomes dominant.