The altered free volume state (AFVS) approach developed by Kulkarni and Mashelkar has been extended to develop a model for viscosity of polymer latices. The effect of variables such as latex concentration, particle size, electrolyte concentration, and shear rate on latex viscosity can be satisfactorily explained within the framework of the AFVS model. The contribution of geometric and electrostatic factors to latex viscosity can be estimated in terms of the model parametersBηand β. Merits of the AFVS approach over the models proposed in the past have been elucidated. A unique superposition is shown to result for the effect of shear rate on the immobilization parameter β for various electrolyte concentrations.