Densities, p, at atmospheric pressure and coefficients of compressibility, k, at p = (10, 25, 50, 75, 100) MPa were measured for aqueous solutions of N,N,N-trimethylglycine (betaine) at T=(278.15, 288.15, 298.15, 308.15 323.15) K. The experimental data have been used to calculate the following volumetric parameters: the apparent molar volume of betaine, V-phi.2, the molar isothermal compression, K-T,K-m, and the molar isobaric expansion, E-p,E-m, of solutions at all pressures and temperatures studied. Some parameters for infinite dilute solution of betaine in water were also obtained such as limiting partial molar volumes, IT, limiting partial molar isothermal compressions, K-T,2(infinity), and limiting partial molar isobaric expansions, E-P,2(infinity). The variation of all these parameters with composition, temperature, and pressure were discussed from the viewpoint of intermolecular interactions in the system.(C) 2014 Elsevier B.V. All rights reserved.