The author’s earlier quantitative interpretations of the nonideal properties of strong electrolytes in aqueous solutions have now been successfully extended to cover the whole range of concentrations. It is shown that (i) nonideality, expressed as osmotic and activity coefficients, is due to the incomplete dissociation and hydration of the electrolyte, (ii) the hydration numbers at the vapor/solution interface and bulk regions are different, (iii) the degree of dissociation has a minimum value at the molality at which the mean ionic activity is unity, and (iv) the molal volume and the molal dissociation constant depend on the volumes of ions and ion pairs. Simple quantitative relations, supporting graphs, and tables of data for NaCl(aq) at 25 degrees C are provided.