The vapor pressure of H 2 O(1)-polyethylene glycol 400(2)polyethylene glycol 6000(3) solutions was evaluated experimentally in a temperature range between 318.15 and 348.15 K and in a broad range of concentrations. The dependence of the solvent activity on composition was evaluated and correlated by means of a polynomial expression, in terms of concentrations, volumetric and mass fractions, and temperature, obtaining in all cases standard deviations less than 0.0086 and 0.0106 for a 1 (ϕ 2 ,ϕ 3 ,T) and a 1 (w 2 ,w 3 ,T), respectively.