Copolymeric hydrogels of poly(2-hydroxyethyl methacrylate-co-acrylamide) [p(HEMA-co-A)] crosslinked with ethylene glycol dimethacrylate, with a high equilibrium degree of swelling (37±65 wt%) in saline solution (NaCl 0.9 wt%) were synthesized as devices for controlled release of cytarabine (ara-C). Two compositions of the copolymer, each with a different degree of crosslinking have been studied, HEMA80/A20 and HEMA60/A40. The antineoplasic drug was included in the feed mixture of polymerization, and discs 3.7 AE 0.4 mm thick and 11.8 AE 0.2 mm in diameter with 5±40 mg (1.0±8.3 wt%) of ara-C were obtained. The diffusion studies followed Fick's second law. The diffusion coef®cients for swelling of the gels were between 3.60 Â 10 À11 and 15.8 Â 10 À11 m 2 s À1 ; those for release of ara-C were between 0.31 Â 10 À11 and 7.18 Â 10 À11 m 2 s À1 . The activation energies for swelling were in the range 23.4±31.9 kJ mol À1 and those for ara-C release were 42.2±61.6 kJ mol À1 ; their values indicate that the drug release process depends on drug±matrix and drug±water interactions that are in¯uenced by the aqueous solution content and the network size of the gels. Total release of the drug takes place between 17 h from H60/A40/E2 at 310 K and 6 days from H80/A20/E10 at 288 K. Ara-C degradation was not observed either during loading of the gels or during drug release.