Rheological characteristics of linear copolymers of acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (Q9), differing in molar mass and chemical composition, have been studied in distilled water (DW) and industrial water (IW) obtained from a paper mill. For all copolymers, the shear viscosity, mu, was much lower as the ionic strength of the water increased, with near Newtonian behaviour observed at high ionic strengths. In DW, the polymer solutions were yield pseudoplastic. Comparison of the behaviour of all flocculants at the same shear rate in the two media was accomplished by modelling the rheological data.