The use of correlation-gas chromatography to measure the vaporization enthalpy {Delta(l)(g)H(m)(298.15 K)} of complex mixtures is demonstrated using RJ-4, a high-energy-density rocket fuel, as a test sample. RJ-4 consists of a complex mixture of exo- and endo-dimethyltetrahydrodicyclo-pentadienes. A value of 55.3 +/- 0.9 kJ.mol(-1) has been obtained for the mixture. Correlation-gas chromatography is applicable in obtaining the vaporization enthalpy of any complex mixture of materials that will pass through a gas chromatograph and for which vaporization enthalpies of suitable standards are available. Once the temperature dependence of each component is established, the results can be used to determine the vaporization enthalpy at any composition.