A critical evaluation of the mean activity &ggr;±, and osmotic coefficients, &fgr;, of aqueous alkali metal nitrites at 298.15 K is presented for the molality range from dilute to saturation. Osmotic coefficients were calculated from static vapor pressure measurements. A nonlinear least‐squares program was used to fit &fgr; data as a function of molality. Several equations describe the osmotic coefficient, the mean activity coefficient, and the excess Gibbs energy as a function of the square‐root of molality for each slit. The scientific literature was covered through March 1979.