The sedimentation behavior of rutile and selected organic pigments dispersed in polymer solutions has been interpreted in terms of acid-base interactions at the polymer/pigment interface. The acid-base information was obtained from inverse gas chromatography. Moderate strengths of acid-base interaction were beneficial to the stability of dispersions, whereas both the absence of and excessive interaction resulted in the rapid deposition of solids. The effect is associated with the orientation of adsorbed polymer molecules, which must provide an adequate steric (entropic) barrier for the aggregation and deposition of solids. Implicated is the balance of interaction forces at pigment/polymer and polymer/solvent contacts. Rheological data for the dispersions have been used to obtain a parameter related to the thickness of the adsorbed polymer layer, by way of amplifying on the state of the pigment/polymer interface.