To predict partitioning of proteins between a temperature- and pH-sensitive hydrogel and its surrounding aqueous solution, it is appropriate to use Schnitzer’s method for determining solute partitioning based on size exclusion and the cell model for polyelectrolyte solutions. The mean-pore size of the hydrogel is calculated using the method of Peppas el al. The charge of the network, which depends on pH and salt concentration, is calculated using weak-polyelectrolyte-titration theory. De Gennes’ scaling relation and Odijk’s wormlike model are used to determine the persistence length and the radius of gyration of the polyelectrolyte chain in the hydrogel. For N-isopropylacrylamide gels copolymerized with sodium acrylate or 2-dimethylaminoethyl methacrylate, predicted partition coefficients for cytochrome-C are in semiquantitative agreement with experiment.