The adsorption isotherms of HCH on coconut shell based activated carbon type NP-5 at constant temperature have been experimentally measured. The porous properties such as, the density, BET surface area, pore size, pore volume along with pore distribution of NP-5 have been determined. The Freundlich's, Langmuir's, Temkin, Jovanovic and BETs adsorption isotherm models describe of experimental data within the acceptable error ranges. The Freundlich, Jovanovic and Langmuir models were fitting better the experimental data. The shape of these isotherms indicates that the HCH is adsorbed as a monolayer and that there is no strong competition between the pesticide molecules and water to occupy the adsorption surface sites. (C) 2011 Elsevier Ltd. All rights reserved.