Activated carbons were prepared from olive oil solid wastes by treatment in different schemes: impregnation with H3PO4 followed by pyrolysis at 300-700 degreesC, by steam pyrolysis at 600-700 degreesC, or by conventional steam activation at 850 degreesC. Porosity characteristics were determined by analysis of nitrogen adsorption isotherms, and carbons of widely different properties and surface pH values were obtained. Decomposition of H2O2 in dilute unbuffered solution was followed by measuring evolved oxygen volumetrically. First-order kinetics was followed, and the catalytic rate coefficients were evaluated. The carbons tested showed appreciable activity where evolved oxygen attained approximate to 10% of the stoichiometric amount in I h. The degree of decomposition showed inverse dependence on surface area, pore volume and mean pore dimensions. The chemical nature of the surface, rather than the porosity characteristics, was the principal factor in enhancing the disproportionation of H2O2 on the activated carbon surface.