The vapor pressure of aqueous solutions of sodium dodecyl sulfate (SDS) + 0.1 mass % polyacrylamide (PAM) and SDS + 0.1 mass % PAM + 0.1 M NaOH were measured at 298.15 K, 308.15 K, and 318.15 K, and the concentration of SDS (m(SDS)) was up to 50 mmol/kg. The activity coefficient of water in the solution was calculated. The surface tension of the solutions was also determined. The results show that the effect of the solutes on the vapor pressure of water is very limited under the experimental conditions although the surface tension changes significantly with SDS concentration.