Ultrasonic velocity and density values of L-phenylalanine, L-leucine, L-glutamic acid, and L-proline + 2 mol.L-1 aqueous NaCl and 2 mol.L-1 aqueous NaNO3 solutions have been measured for several molal concentrations of amino acids at different temperatures from T = (298.15 to 328.15) K. The isentropic compressibility values (kappa(s)) have been computed using the ultrasonic velocity and density data. The kappa(s) values decrease with an increase in the molal concentration of amino acids as well as with temperature. The trends of variation of kappa(s) with the variation in molal concentration of amino acids as well as with temperature have been discussed in terms of various interactions operative in solutions.