Ultrasonic velocity and density of binary mixtures containing aniline, toluene, and n-butanol were measured at 303 K. Thermodynamic parameters such as molar volume, adiabatic compressibility, intermolecular free length, and excess values were calculated, revealing molecular interactions within the mixtures. Results support the observations using R-K type equation fittings. © TÜBITAK. © 2011 Elsevier B.V., All rights reserved.