This paper reports the pressure-temperature conditions for the three-phase aqueous liquid + hydrate + vapor equilibrium in the structure I hydrate forming water + methylfluoride water system and for the four-phase aqueous liquid + hydrate + liquid hydrocarbon + vapor equilibrium in the water + methylcyclohexane + methylfluoride system. The pressure and temperature ranges of the present measurements are from (0.267 to 3.582) MPa and from (273.5 to 296.2) K in the water + methylfluoride system and from (0.185 to 2.703) MPa and from (273.7 to 294.2) K in the water + methylcyclohexane + methylfluoride system. The crystallographic structure of the hydrate formed in the water + methylcyclohexane + methylfluoride system at 279.7 K was determined to be structure H based on the X-ray diffraction measurement. The phase equilibrium data suggest the formation of structure I simple methylfluoride hydrate at temperatures above 289 K in the system with methylcyclohexane.