Isentropic compressibilities K(S), excess isentropic compressibilities K(S)E, and excess volumes V(E) have been determined from the densities and speeds of sound for eight binary mixtures of (tri-n-butylamine, tri-n-hexylamine, tri-n-octylamine, or tri-n-dodecylamine + cyclohexane or benzene) at 303.15 K. The values of V(E) and K(S)E are more positive for mixtures with benzene than for the mixtures with cyclohexane. The experimental results have been analyzed by the Prigogine-Flory-Patterson theory.