N-Vinyl-2-pyrrolidone and 2-hydroxyethyl methacrylate in both the absence and the presence of ethylene glycol dimethacrylate have been copolymerized to high conversion by 7-irradiation. The resultant xerogels were swollen to equilibrium in water to yield hydrogels. The effects of monomer composition and concentration of added cross-linking agent on the swelling behavior and mechanical properties of these hydrogels at 294 K were investigated, the latter involving measurements of stress (compression)-strain. The findings were interpreted on the basis of terpolymer compositional drift as predicted by the Q—e scheme. Inhomogeneous cross-linking of the copolymer network was noted particularly at high contents of N-vinyl-2-pyrrolidone.