Densities of aqueous mixtures of KCI with NaBr are reported at Ionic strengths of 0.5, 1, 2, 3, and 4 mol kg'1 and at 298.15 K from pure KCI to pure NaBr solutions. The excess volumes of mixing, which are negative, can be fitted to Friedman's equation. Mixing experiments at equlmolal concentration and Ionic strengths 1 and 4 mol kg'1 were also conducted at 278.15 and 318.15 K. The results Indicate weak temperature dependence of the excess volumes. The densities of these mixtures can be estimated accurately with Young's rule, If the excess volumes are taken Into account.