Effects of inorganic salts on viscosities of dimethyl sulphoxide (DMSO) solutions of acrylonitrile(AN)/N-vinylpyrrolidone(N-VP) copolymer are discussed. Viscosity was determined by the rotary viscosimeter. It was shown that the solution viscosity decreases quickly with addition of KCl and NaCl and the effect of NaCl is more prominent than that of KCl. As concentration of KCl and NaCl went beyond 0.025 mol/L, the viscosity showed a trend of increase. The viscosity increased considerably with addition of FeCl3 and CuCl2. Changes in solution viscosity became less obvious with addition of ZnCl2. As temperature increased, the viscosity of the copolymer solution containing NaCl decreased most quickly and the copolymer solution consisting of FeCl3 showed the slowest decrease. (C) 2003 Wiley Periodicals, Inc.