A simple equation has been proposed to describe the activity coefficients, gamma (+/-), of the salts in aqueous and nonaqueous solutions and their mixtures. In principle, the equation involves the Debye-Huckel theory for accounting the long-range interaction forces! whereas the short-range interaction forces are attributed to the solvation process. The solvation process is described by two adjustable parameters, viz., alpha (1) and alpha (2). With the use of these two parameters, it is possible to correlate with good accuracy the activity coefficients of numerous salts of different charge types in water. The proposed equations have also been extended to nonaqueous solutions and the mixed solvents with good accuracy. Fitting of activity coefficient data by the proposed model to high temperatures for a variety of salt solutions demonstrates its applicability under elevated conditions. The solvent activities in salt solutions can also be predicted with excellent accuracy using alpha (1) and alpha (2) specific to a salt solution.