The excess heat capacities, C-P(E), of binary 1-methyl pyrrolidin-2-one (i) + pyridine or alpha- or beta- or gamma-picoline (j) mixtures have been measured as a function of composition at 293.15, 298.15 and 303.15K using micro differential scanning calorimeter (Model - mu DSC 7 Evo). The C-P(E) data have been fitted to Redlich-Kister equation to calculate binary adjustable parameters and standard deviations. The measured property of the studied mixtures has been analyzed in terms of Graph (which deals with the topology of the constituent of mixtures) theory. It has been observed that Graph theory describes well the C-P(E) data of the investigated binary mixtures. (C) 2013 Elsevier B.V. All rights reserved.