The coil-globule transition of poly(N-isopropylacrylamide) (systematic name: poly[1-(isopropylaminocarbonyl)ethylene]) has been viscometrically investigated in low-concentration aqueous sodium dodecyl sulfate solution. In this environment, even if the macromolecular coils collapse as the temperature increases above the lower critical solution temperature of the polymer, 34 degrees C, the polymer does not precipitate. II seems that the hydrophobically collapsed macromolecular coils do not aggregate, but remain in solution with the aid of surface charges supplied by surfactant ions adsorbed through hydrophobic interactions.