Prediction of swelling behaviour of hydrogels containing diprotic acid moieties, sensitive to pH and ionic strength changes of the swelling medium, was investigated. The equations derived for the prediction of the theoretical swelling curves are based on the phantom network theory of Erman et al. and the approaches of Peppas er al. For all predictions, a number of polymer-based parameters, solution property parameters and polymer-solvent combination type parameters were evaluated typical of dicarboxylated copolymers. The advantages of the derived equations for the determinations of average molecular weight between the cross-links and also a polymer-solvent interaction parameter have been exemplified.