The literature provides several size-exclusion theories to predict solute exclusion by highly swollen hydrogels. Theoretical calculations are compared to the experimental data of Walther et al. (1993) for partitioning of poly(ethylene glycol)s and poly(ethylene oxide)s of various molecular weight into hydrogels made of poly-N-isopropylacrylamide or poly-2-hydroxyethyl methacrylate/dimethylaminoethyl methacrylate. Experimental size-exclusion curves can be correlated almost equally well by theories which characterize the gel as a collection of pores or of fibers; differences between these two theories are important only for partition coefficients near zero or unity. The experimental data of Walther et al. can be predicted best by Schnitzer’s uniform pore model.