The flexibility and selectivity of size exclusion chromatography (SEC) for protein purification can be modified by adding non-ionic micelle-forming surfactants to the mobile phase. The micelles exclude proteins from a liquid phase similar to the exclusion effect of the polymer fibers of the size exclusion resin. This surfactant-aided size exclusion chromatography technology (SASEC) is demonstrated on the separation of two model proteins; bovine serum albumin (BSA) and myoglobin (Myo). The effect of the added surfactants on the distribution behavior of the proteins is predicted adequately by a size exclusion model presented in this paper.