A knowledge of the theology of titanium dioxide pigment suspensions and the variation with processing conditions is essential for optimum plant operation and in ultimate paint production. In this paper the influence of pH, solids concentration, and particle size on the theological properties of four commercial TiO2 pigment suspensions is reported. The suspensions exhibit pseudoplastic behavior, conforming to the power-law model in the shear rate range investigated. Extreme sensitivity with pH was observed, whereby the suspension viscosity can be changed by as much as an Order of magnitude with pH variation at constant volume fraction. Also, the pH at maximum viscosity coincides with the isoelectric point, independent of solids concentration. The maximum viscosity (viscosity at the isoelectric point) increases exponentially with solids concentration and increases with decreasing particle size. The important outcome from the investigation is the dependence of theology on the compressional history used for dewatering the suspensions. Two identical pigments from two different filtration devices exhibited a large difference in their viscosity, as a consequence of being subjected to different compressional forces. Finally, the presence of a monolayer coating of organic on the pigment surface illustrates how to lower the observed suspension viscosity with steric stabilization.