Excess molar enthalpies (H-M(E)) at 298.15 K and ambient pressure have been measured as a function of composition for the binary liquid mixtures of dimethylsulfoxide (DMSO) with chloroethanes and chloroethenes. The chloroethanes include 1,2-dichloroethane, 1,1,1-trichloroethane and 1,1,2,2-tetrachloroethane and the chloroethenes are trichloroethene and tetrachloroethene. The H ME values for the above mixtures have been measured by a Paar 1451 solution calorimeter and are negative over the whole range of composition in all the binary mixtures except in the binary system of DMSO with tetrachloroethene, whereas the HE is positive over the entire range of composition. The experimental results have been correlated using the Redlich-Kister (R-K) polynomials and the results are interpreted on the basis of possible hydrogen bonding between unlike molecules and changes in molecular association equilibria as well as structural effects for these systems. The excess molar enthalpy data have also been correlated with the Peng-Robinson (PR) as well as the Patel-Teja (PT) equations of state (EOS) and also the activity coefficient models of the Wilson and the NRTL. (C) 2007 Elsevier B.V. All rights reserved.