This study aims to clarify the effect of adsorbability, desorbability, biodegradability and activated carbon type on the extent of bioregeneration in the treatment of phenol. For this purpose, four different activated carbon types; one thermally activated and one chemically activated powdered carbon (PAC), and their granular countertypes (GAC) with similar physical characteristics were used. Adsorption isotherms showed that the thermally activated carbons, either in powdered or granular form, were better adsorbers for phenol than the chemically activated ones. However, adsorption was more irreversible in the case of thermally activated carbons. Bioregeneration of chemically activated carbons were found to be higher in accordance with their higher reversibility of adsorption showing that bioregeneration was controlled by the reversibility of adsorption. Bioregeneration efficiencies for the thermally activated carbons were much higher than their efficiencies of total desorbability. This indicated that some exoenzymatic reactions might have occurred so that phenol was bioregenerated more than expected.