The main thermodynamic parameters were evaluated for the dextran/ methoxy ethylene glycol (MEG) system by viscosity measurements at 25, 30, 35, 40, and 45 degreesC. The long-range and short-range interaction parameters were determined by extrapolation methods, i.e. Kurata-Stockmayer-Fixman, Berry, and Inagaki-Suzuki-Kurata equations. Calculated values, as well as the unperturbed root-mean-square end-to-end distance and hydrodynamic expansion factor, were interpreted mainly on the basis of hydrogen-bond formation between polymer segments and dextran/MEG molecules in solution. The thermodynamic interaction parameter was also evaluated for the same system. The theta temperatures were obtained from the temperature dependence of the interaction parameter, dependence of (1/2-chi) and the second virial coefficient in the temperature interval of 25 and 45 degreesC for the system and quite a good accordance was indicated with the calculated values evaluated via extrapolation and interpolation methods.