Equipment for high-pressure multiphase-equilibrium measurements has been constructed and tested. The apparatus is capable of operating at pressures p up to 60 MPa and at temperatures T from 270 K to 373 K. (Vapour + liquid + liquid) equilibrium compositions have been measured for (methane + methylcyclohexane + ethan-1,2-diol + water) at p = 7 MPa and at T = 275 K, 297 K, and 323 K. The experimental results are in fairly good agreement with other published experimental results at T = 275 K and 323 K. The measured phase compositions and phase volumes have been compared with calculations using the Peng-Robinson and a modified Redlich-Kwong-Soave equations of state. The calculated compositions for the major components in all three phases agree moderately well with the experimental values, but the calculated compositions for the minor components in the liquid phases are seriously in error. Measured and calculated phase volumes are in approximate agreement.