Crosslinked copolymers of methyl methacrylate with N-vinyl-2-pyrrolidone of various compositions were prepared to high conversion by gamma-irradiation and swollen in water to yield equilibrium water contents of 15-76 wt%. Differential scanning calorimetry was used to probe the states of water in the hydrogels prior to equilibrium swelling. Diffusion coefficients of water decreased about 100-fold as the effective crosslinking density of the polymers increased by the same factor. The relative uptake of the non-freezing water was found to be more rapid than that of the total freezing water.