The adsorption isotherms of naphthalene, phenanthrene, hexachlorobenzene, and pentachlorophenol on activated carbon in the presence of supercritical carbon dioxide were determined at 308 and 318 K and at pressures around 100 atm using an experimental technique based on frontal analysis chromatography. The isotherms were modeled by the Freundlich equation, and the heats of adsorption of these organics on carbon were extracted from the temperature dependency of the initial slopes of the isotherms. The heats of adsorption were found to be in the range 4–8 kcal/mol. The amount of organic adsorbed on carbon was found to be independent of the nature of organic. The desorption of these organics from activated carbon with supercritical carbon dioxide was also investigated in the same temperature and pressure ranges and were modeled successfully by the local equilibrium theory. The extremely long tails observed in the desorption profiles can be attributed to the steepness of the initial slopes of the adsorption isotherms which limit the concentration of the organic in the fluid phase to an extremely small value. © 1993, American Chemical Society. All rights reserved.