P(NIPA-NVP) and P(NIPA)/PVP interpenetrating polymer network hydrogels were synthesized by radiation polymerization in this article. Acetylsalicylic acid proved a model drug of salt resistance. Drug-controlled release of these hydrogels containing acetylsalicylic acid was investigated. Influences of radiation dose, feed composition on the lower critical solution temperature (LCST), swelling behavior, salt dissolubility, and controlled release effect were discussed. The preferable preparation conditions for the titled aim were dose rate of 1 KGy/h, total dose of 30 KGy, feed monomer ratio of NIPA:NVP between 1:1 and 4:1, and total monomer concentration of 10%. As NVP content of the hydrogel increased, LCST rose, swelling ratios increased, salt resistance improved, and both swelling and deswelling rates slowed. Due to the ability of forming association complex, these hydrogels had the function of solubilization that made the drug release of difficult dissoluble medicine effective. These hydrogels had a higher drug release at physiological environment. The experimental results showed that these hydrogels were promising materials for causing solubilization and developing a long-term controlled release system. (C) 2003 Wiley Periodicals, Inc.