Adsorption of sulphur dioxide (SO2), a common gaseous pollutant, on oil-palm-shell activated carbon in a fixed bed was studied in this paper. Oil-palm shell is an abundant agricultural solid waste in tropical countries like Malaysia and Thailand. The effects of fixed-bed length, SO2 gas superficial velocity, adsorbent particle size and internal pore structure on fixed-bed performance were investigated. Some characteristic parameters such as the breakthrough time, tau(0.05), exhaustion time, tau(0.95), length of mass transfer zone, L-MTZ, adsorptive capacity, W, and adsorption rate constant, K, were derived from the breakthrough curves. Tests Of SO2 adsorption onto activated carbons prepared from oil-palm shells pre-impregnated with potassium hydroxide (KOH) and phosphoric acid (H3PO4) of different concentrations were also carried out. It was found that the fixed-bed performance was not only dependent on the operating conditions and the textural properties of the adsorbent but was also influenced by the surface chemistry of the adsorbent, which was related to the type and concentration of the impregnating agent. In general, the quality of oil-palm-shell activated carbon prepared by CO2 activation is comparable to that of a commercial product, and the samples prepared from oil-palm shell with KOH pre-impregnation are more suitable for the removal Of SO2 gas. (C) 2002 Elsevier Science B.V. All rights reserved.