Molar excess volumes V-ijk(E) and speeds of sound, u(ijk) of 2-pyrrolidinone (i) + benzene (j) + toluene or o- or p-xylene (k) ternary mixtures have been measured as a function of composition at 308.15 K. The observed speeds of sound data have been utilized to calculate their excess isentropic compressibilities. The observed data have been fitted to Redlich-Kister equation to calculate ternary adjustable parameters and standard deviations. Molar excess volumes, V-ijk(E) and excess isentropic compressibilities, (kappa(E)(S))(ijk) data for the investigated mixtures have been analyzed in terms of Graph theory and Flory theory. It has been observed that V-ijk(E) and (kappa(E)(S))(ijk) values calculated by Graph theory compare well with their corresponding experimental values. (C) 2009 Elsevier B.V. All rights reserved.