Hydrophobically modified acrylic acid (AA) hydrogels containing fluorocarbon hydrophobic group and hydrocarbon-modified gels using 2-(N-ethylper-fluorooctanesulfoamido) ethyl methacrylate (FMA), and lauryl acrylate (LA) respectively, 2-(N-ethylperfluorooctanesulfoamido) ethyl methacrylate (FMA), were synthesized. Acetaminophen, with analgesic and antipyretic property, acted as the model drug. Swelling, rheological, and mechanical properties of the gels were investigated. Fluorocarbon-modified gels show the stronger hydropho-bicity than do the hydrocarbon-modified gels, which affected the gel's drug-releasing behavior. The drug release behavior depends on pH of the solution medium, the type of hydrophobic modification and the amount of hydrophobes. Hydrophobically modified PAA gels have higher storage modulus E' than the unmodified PAA gels. (9 2007 Wiley Periodicals, Inc.