To study the regeneration of activated carbon used for removal of dioxins from flue gas, the behavior of adsorbates in activated carbon and the adsorptive capacity of the regenerated activated carbon were investigated by repeated exposure to flue gas and regeneration by thermal treatment in a nitrogen atmosphere. Adsorbed dioxins was decomposed in the activated carbon without desorption into the gas phase by the thermal treatment at 400degreesC under nitrogen. Dioxins did not accumulate in the activated carbon in the repeated regeneration tests. Chlorobenzen and chlorophenol showed similar behavior to dioxins. Sulfur also did not accumulate in the activated carbon, but mercury tended to accumulate slightly, and chlorine tended to accumulate remarkably. The adsorptive capacity of the activated carbon for dioxins and sulfur did not change during the repeated regeneration tests, but that for mercury and chlorine tended to decrease due to their accumulation in the activated carbon. The test results showed that the thermal treatment at 400degreesC under nitrogen was effective for regeneration of activated carbon used for removal of dioxins from flue gas.