The catalytic effect of inorganic species, within the ash, on the CO2 gasification of three South African coals containing similar carbon-structural properties (elemental, structural and petrographical properties) was assessed. The reactivity of the coals with a particle size between 150 and 250 mu m was determined in a thermo gravimetric analyser. The reactivity was measured at temperatures between 900 and 1000 degrees C, pressures between 1 and 10 bar, and fractions of CO2 between 10 and 30%. For the selected coals, the reactivity decreased with ash content, and was found to be dependent on the composition of the ash. Specifically, the reactivity increased with calcium and magnesium content and alkali index. (C) 2011 Elsevier B.V. All rights reserved.