The present work describes a method that allows rapid measurement of both VLE and VLLE isotherms. Samples of the various phases are taken from a high-pressure autoclave equipped with windows using a movable needle. The samples are sent directly into a GC that is calibrated using pure compounds. The procedure allows for the measurement of a full isotherm with 5 to 10 data points for all phases during one working week. The method has been validated by measuring the Systems CO2 + CH3OH and CO2 + (CH3)(2)O and comparing with literature data. Thereafter, a range of systems composed of the five components N-2, CO2, (CH3)(2)O, H2O, and CH3OH has been measured. This work contains new experimental data for the systems CO2 + CH3OH, N-2 + (CH3)(2)O, CO2 + (CH3)(2)O, N-2 + (CH3)(2)O + H2O, CO2 + (CH3)(2)O + H2O, CO2 + (CH3)(2)O + H2O + CH3OH, N-2 + (CH3)(2)O + H2O + CH3OH, and N-2 + CO2 + (CH3)(2)O + H2O + CH3OH, in the temperature range 25 to 45 degreesC and the pressure range 3 to 105 bar.