A chromatographic method is used to measure ovalbumin-lysozyme and BSA-lysozyme interactions in aqueous salt solutions as a function of solution conditions (pH, ionic strength, salt type). In this method, one protein is immobilized on the support surface, and the other, dissolved in a buffer/electrolyte solution, flows over that surface. The retention time provides a measure of immobile/mobile protein-protein interactions. Trends in ovalbumin-lysozyme interactions suggest that they are primarily electrostatic. The identity of the electrolyte has a strong influence on the magnitude of the interaction. Assuming a potential of mean force that contains a hard sphere, electrostatic, and square-well potential, experimental results are used to fit the square-well depth. For BSA-lysozyme interactions, the square-well depth depends on which protein is immobilized on the solid phase. (C) 2004 Published by Elsevier B.V.