Apparent molar volumes (174,) and viscosity B-coefficients for citric acid in (0.001, 0.003, and 0.005) mol . dm(-3) aqueous cetrimonium bromide (N-cetyl-N,N,N-trimethyl ammonium bromide, C(19)H(42)NBr) solutions have been determined from solution density and viscosity measurements at T = (298.15, 308.15, and 318.15) K and p = 0.1 MPa as a function of the concentration of citric acid. The apparent molar volumes have been extrapolated to zero concentration to obtain the limiting values at infinite dilution (V(phi)(0)), using the Redlich-Meyer equation, and the obtained parameters have been interpreted in terms of solute-solvent interactions. The viscosity data were analyzed using the Jones-Dole equation, and the derived parameters A and B have also been interpreted in terms of solute-solute and solute-solvent interactions, respectively, in the mixed solutions. The structure-making or -breaking ability of the electrolyte has been discussed in terms of sign of dB/dT. The activation parameters of viscous flow for the ternary solutions studied have also been calculated and explained by the application of transition state theory.