In this study, the equilibrium conditions of methane hydrate is measured experimentally in the presence of 1-ethyl-3-methyl-imidazolium chloride (EMIM-Cl) and 1-hydroxylethyl-3-methyl-imidazolium chloride (OH-C2MIM-Cl) solutions. These two ionic liquids are chosen to study their performances as low dosage hydrate inhibitors. To study the effect of these ionic liquids on the equilibrium phase boundary of methane hydrate, several experiments are conducted in a pressure range of 4-12MPa. In addition, the equilibrium data in EMIM-Cl solutions are modeled using an equation that takes into account the effects of electrolyte on the activity of water. Results show that phase boundary of methane hydrate is shifted toward lower temperature at constant pressure from 0.1 to 1.5K in the presence of these ionic liquids. This temperature shift, however, becomes more significant at pressures higher than 70MPa. © 2012 Elsevier B.V.