The interactions of hydrophobically modified polyelectrolytes poly(acrylamide-sodium acrylic acid-N-(4-butyl)phenylacrylamide [P(AM-AA-BPAM)] with anionic (sodium dodecyl sulfate), cationic (cetyl trimethyl-ammonium bromide), and nonionic (tetradecyldimethyl-aminoxid) surfactants were studied via solution rheology, surface tension, and atomic force microscopy measurements. Viscosity measurements indicated that the intermolecular association of the polymer was greatly enhanced by the interaction with the surfactants, especially the oppositely charged surfactants with both a hydrophobic association and an electrostatic attraction. The greatest viscosity increase was realized with the addition of such oppositely charged surfactants. (C) 2003 Wiley Periodicals, Inc.