Chlorofluorocarbon (CFC) replacements have recently been used for their lower stability and because they have carbon-hydrogen bonds, which means that their atmospheric lifetime is expected to be much shorter than those of CFCs, The adsorption properties of 1, 1, 2-trichloro-1, 2, 2-trifluoroethane (CFC113) and its replacement compounds, 1, 1-dichloro-2, 2, 2-trifluoroethane (HCFC123), 1, 1-dichloro-1-fluoroethane (HCFC141b), and 1, 1-dichloro-1, 2, 2, 3, 3-pentafluoropropane (HCFC225ca) on four kinds of activated carbons were investigated. The amount of CFC and HCFCs adsorbed on the activated carbon was concluded to depend upon the number of chloride and carbon atoms in their molecules. The adsorption isotherms of inhalational anesthetics (halothane, chloroform, enflurane, isoflurane, and methoxyflurane) on the activated carbon were measured to evaluate the action mechanism of inhalational anesthesia. The adsorption isotherms of CFC, HCFC, and the inhalational anesthetics were fitted to the Freundlich equation. The Freundlich constant N was well correlated with the minimum alveolar concentration (MAC) of the inhalational anesthetic : 1 MAC means that 50% of the patients will not move during a surgical operation. The adsorption mechanism of inhalational acesthetics on the surface of the activated carbon is concluded to be similar to the adsorption mechanism on a nerve cell. The anesthesia of CFC replacements can be estimated by the Freundlich constant N of the adsorption isotherms.