The metal ion distributions of a solution of poly(sodium 4-styrenesulfonate) in the presence of Cd2+ and Na+ ions are obtained by ultrafiltration. The results are used to evaluate the Manning＇s two-variable counterion condensation theory concerned with long-range interactions. The original theory results are insufficient to explain the metal ion distributions obtained, and shea-range interactions have to be included. We also propose the inclusion of the influence of the polymer conformations in the theory.