Polymer-surfactant interactions have been studied by Gel Permeation Chromatograhy in order to include a dynamic aspect. Associative interactions can be identified and studied with this method. Also quantitative measurements on the amount of surfactant associated with the polymer have been performed. Association between PEO and ethoxylated sulfonates decreases when the number of EO-groups in the surfactant increases. For more than 3 EO-groups the association with PEO disappears. When there are repulsive interactions, like in (P-S-)-systems, the results are difficult to interpret. A (P-S-) -system is separated in a GPC column due to osmosis and size exclusion. PS-interactions cannot explain the surprising core flood results.