Volumetric and acoustical parameters are reported for glycylglycine in aqueous NiCl2 solution at T = (288.15-318.15) K. The apparent molar volumes and isentropic compressibilities were calculated from the experimental data of ultrasonic velocity and density. Together with these, excess isentropic compressibility (kappa(E)(S)), excess free volume (V-f(E)), excess intermolecular free length (L-F(E)) and deviations of ultrasonic velocity (Delta u) were obtained. The results are interpreted in terms of molecular interactions. The results show that the cation and anion play a significant role in influencing the behavior of glycylglycine in aqueous solutions. These effects were also attributed to the doubly charged behavior of glycylglycine and to the formation of physically bonded ion-pairs between charged groups of glycylglycine and cation and anion of the electrolyte. (C) 2010 Elsevier B.V. All rights reserved.