The performance of 1-ethyl-3-methylimidazolium chloride (EMIM-Cl), one of novel ionic liquid inhibitors for gas hydrate, in inhibiting methane hydrate at low and high ionic liquid concentrations is investigated in a pressure range of 10-20 MPa. Experiments on methane hydrate dissociation conditions in the presence of mixed ionic liquid and conventional inhibitors, such as sodium chloride (NaCl) and monoethylene glycol (MEG), as well as a mixture containing two ionic liquids, EMIM-Cl and 1-ethyl-3-methylimidazolium bromide (EMIM-Br), are also performed to investigate any possible synergistic effects. It is observed that single component solutions of EMIM-Cl demonstrate a progressive increase in inhibition effect with increasing concentration, which may surpass the effectiveness of MEG at high concentrations. Although the thermodynamic inhibition performance of the mixtures of EMIM-Cl and MEG does not show any synergistic effects at low pressures, it does at higher pressures. The mixture of EMIM-Cl and EMIM-Br also shows a synergistic effect at higher pressures. Unlike MEG or NaCl, inhibitors containing EMIM-Cl or EMIM-Br demonstrate an increase in inhibition effectiveness as pressure increases. (C) 2012 Elsevier Ltd. All rights reserved.