The methylcyclohexane + Xe hydrate system has been investigated in a temperature range from 274 to 291 K and pressure up to 1 MPa. The structure-H (s-H) type hydrate changes to the structure-I (s-I) type of Xe hydrate at 281.5 K. The overall enthalpy of s-H hydrate formation has been evaluated using the Clapeyron equation. The transition enthalpy change from s-H to s-I is estimated to be about 70 kJ/mol for unit amount of s-H hydrate. Neither cis-1,3-dimethylcyclohexane nor cis-1,4-dimethylcyclohexane generates the s-H hydrate in the presence of Xe.