Poly(N-vinyl-2-pyrrolidone) (PVP) is widely used in medicine due to its high biocompatibility. In this study, itaconic acid (IA) was co-polymerized with N-vinyl-2-pyrrolidone (NVP) monomer to prepare the pH sensitive hydrogels. These copolymer hydrogels were prepared using ultra-violet (UV) induced methods at ambient temperature. Monomer and cross-linking agent (NAP-methylene-bisacrylamide (MBAAm)) concentration effects on preparation of this copolymer hydrogel were investigated using swelling, FIF-IR, and SEM. The prepared copolymer hydrogel is highly pH sensitive. The percentage swell of the copolymer hydrogels was found to increase from 150 to 3011% as the pH value of the swelling solution varied from 4 to 10. These pH sensitive copolymer hydrogels present a promising approach for drug delivery applications. (c) 2004 Elsevier B.V. All rights reserved.