A simultaneous study of acid-base and solubility equilibria of acetylsalicylic acid has been carried out by potentiometry with a glass electrode in NaCl and KNO3 at several ionic strengths and 25 degreesC. The dependence of the stoichiometric equilibrium constant on ionic strength has been analyzed according to different specific interaction theories. The experimental data also allow one to estimate both the salting coefficient of acetylsalicylic acid in the studied electrolytes and the specific interaction parameters of acetylsalicylate ion with cations of the support electrolyte.