The hydrophobically modified polyelectrolytes were prepared by a micellar technique from acrylamide, n-alkylacrylamides, and a third monomer, sodium acrylate or sodium 2-acrylamide-2-methylpropanesulfonate. Synthesis and solution properties of the terpolymers were studied. In the synthesis process, the type and amount of surfactant and anionic monomers influenced their solution behavior greatly. The terpolymers showed strong synergistic viscosification effects between their ions and hydrophobic groups. Their aqueous brine solutions exhibit high viscosity at low polymer concentration and can maintain the viscosity during aging at a high temperature (80 degreesC).