The Wagner-Pruss equation for the saturation pressure of pure water is modified for the calculations of the vapor pressures of aqueous NaCl and CaCl2 solutions. The modified equation is applicable to the temperatures from 273.15 to 643 K and to the concentrations up to 30 mass% for aqueous NaCl solution and 18.9 mass% for aqueous CaCl2 solution. The modified equation involves concentration-dependent terms and multiplies the reduced temperature by T-c/647.096, where T-c is the critical temperature of the aqueous solution, in the WagnerPruss equation. (C) 2003 Elsevier B.V. All rights reserved.