Six dialkylimidazolium halide ionic liquids have been investigated for their potential application as novel gas hydrate inhibitors. Their effects on the equilibrium methane hydrate dissociation curve in a pressure range 105-205 bar and the induction time of methane hydrate formation at 114 bar and a high degree of supercooling, i.e., about 25 degrees C, are measured in a high-pressure micro-differential scanning calorimeter. Similar to dialkylimidazolium tetrafluoroborate investigated in our previous work, these ionic liquids are found to shift the equilibrium hydrate dissociation/stability curve to a lower temperature and, at the same time, retard the hydrate formation by slowing down the hydrate nucleation rate. To understand the performance of these ionic liquids in inhibiting the hydrate formation, the electrical conductivity and infrared spectra of ionic liquids are also obtained and analyzed. (C) 2010 Elsevier Ltd. All rights reserved.