Vapor-liquid equilibria were measured for (1) binary mixtures of carbon dioxide with nonane, cumene, propylbenzene, or mesitylene, (2) binary mixtures of propane with nonane, cumene, or mesitylene, and (3) ternary mixtures of carbon dioxide, nonane, and cumene. For the carbon dioxide mixtures, vapor-liquid equilibria were measured at 70 degrees C and at pressures ranging from 3.7 MPa to 12.1 MPa. For the propane mixtures, vapor-liquid equilibria were measured at 104 degrees C and at pressures ranging from 0.9 MPa to 3.7 MPa. It was found that differences in the phase equilibria of the mixtures could be explained primarily by the self-association of the C-9 components. The composition of the C-9 components in the vapor phase compositions were found to be directly related to the volatility (self-association) of the C-9 component. Liquid phase compositions were found to be enriched in carbon dioxide or propane content in the mixtures containing C-9 compounds having the weakest self-association. Also presented in this paper are comparisons of measurements of vapor-liquid equilibria of carbon dioxide + decane and propane + decane with literature data as validation of the two experimental methods used. These measurements were made at 71 degrees C for the carbon dioxide + decane mixtures and at temperatures ranging from 38 degrees C to 120 degrees C for the propane + decane mixtures.