Densities and viscosities of solutions of tetrabutylammonium bromide have been measured in gamma-butyrolactone + water mixtures at various temperatures, (298.15, 303.15, 308.15, 313.15, and 318.15) K. The viscosity data have been analyzed using the Jones-Dole equation. The density data have been utilized to calculate apparent molar volumes, V-phi, and partial molar volumes at infinite dilution, V-phi(0). The behavior of these parameters has been used to investigate the solute-solute and solute-solvent interactions.