Activated carbon fibers (ACFs) were prepared by chemical activation of poly(p-phenylene terephthalamide (PPTA) with phosphoric acid, with a particular focus on the effects of impregnation ratio and carbonization temperature on both surface chemistry and porous texture. Thermogravimetric studies of the pyrolysis of PPTA impregnated with different amounts of phosphoric acid indicated that this reagent has a strong influence on the thermal degradation of the polymer, lowering the decomposition temperature and increasing the carbon yield. As concerns surface chemistry, TPD and chemical analysis results indicated that the addition of phosphoric acid increases the concentration of oxygenated surface groups, with a maximum at an impregnation ratio of 100 wt.%. The resulting materials present uncommon properties, namely a large amount of oxygen- and phosphorus-containing surface groups and a high nitrogen content. Porosity development following H(3)PO(4) activation was very significant, with values close to 1700 m(2)/g and 0.80 cm(3)/g being reached for the BET surface area and total pore volume, respectively. The pore size distributions remained confined to the micropore and narrow mesopore (<10 nm) range. (C) 2011 Elsevier Inc. All rights reserved.