In this work the attention was focused on the adsorption and desorption of elemental mercuric on HGR activated carbon produced by Calgon-Carbon Corp. The study was performed in an apparatus at laboratory scale in which Hg0 vapors in a nitrogen gas stream, at a given temperature and mercury concentration, flowed through a fixed bed of adsorbent material. The experiments showed that the adsorption phenomena are faster than the desorption phenomena. SEM micrographs of the fresh carbon and of the carbon after adsorption or desorption had occurred have shown that mercury is adsorbed on the surface on particular sites where high sulfur concentration exists.