To develop carbon-based sorbents to be used in gas-phase mercury removal, the performance of virgin activated carbons (AC) with that of sulfur-impregnated activated carbons was compared. Virgin AC with increased oxygen functional groups was superior in mercury adsorption performance. The adsorption performance of sulfur-impregnated AC depended on the pore characteristics of virgin AC used as raw material and the types of sulfur, rather than on the amount of sulfur impregnated. AC that impregnates sulfur should have a large pore diameter (average pore diameter above 20 A). A method of reactive sulfur impregnation has been developed. With the method, the utilization efficiency of sulfur to mercury adsorption was maximized. (C) 2003 Elsevier Science B.V All rights reserved.