The density (rho) and viscosity (eta) of three amino acids, glycine, L-alanine, and L-valine, have been determined as a function of amino acid concentration in aqueous solutions of 0.1011, 0.3088, and 0.5245 mol.kg(-1) sodium benzoate at temperatures 303.15, 308.15, and 313.15 K. Apparent molar volumes (V-phi), limiting values of apparent molar volumes (V-phi(0)), and transfer volumes (Delta V-t(phi)0) have been calculated from the density data. The viscosity data could be fit to the Jones-Dole equation, and B coefficients and variation of B with temperature dB/dT were obtained at different concentrations and temperatures. Free energies of activation of the solvent (Delta mu(0 not equal)(1)) and solute (Delta mu(0 not equal)(2)) were also calculated by application of the Eyring transition-state theory. The obtained thermophysical data have been interpreted in terms of the structure of the amino acids and their interactions with the sodium benzoate solution.