Analysis of the novel approach for the determination of CPVC's by viscosity measurements shows that the explanation for the dependence of viscosity on pigment volume concentration as given by K.M.A. Shareef and M. Yaseen (J. Colour Soc.8, Oct/Dec 1983, 8-12) is very unlikely. The dependence is either caused by a fortuitous combination of binder viscosity, Einstein coefficient of the pigment, and binder adsorption, or it is on artefact, based on slippage of the spindle in the high viscosity systems, for example.