Large quantities of lignocellulosic residues result from the industrial production of essential oil from vetiver grass (Vetiveria zizanioides) roots. These residues could be used for the production of activated carbon. The yield of char obtained after vetiver roots pyrolysis follows an equation recently developed [A. Ouensanga, L. Largitte, M.A. Arsene, The dependence of char yield on the amounts of components in precursors for pyrolysed tropical fruit stones and seeds, Micropor. Mesopor. Mater. 59 (2003) 85-91]. The N-2 adsorption isotherm follows either the Freundlich law KFP alpha which is the small a equation limit of a Weibull shaped isotherm or the classical BET isotherm. The surface area of the activated carbons are determined using the BET method. The K-F value is proportional to the BET surface area. The a value increases slightly when the bum-off increases and also when there is a clear increase in the micropore distribution width. (c) 2006 Elsevier B.V. All rights reserved.