The effect of process variables such as coal preoxidation, pyrolysis conditions and activating agent -carbon dioxide and steam- on the preparation of active carbons was studied. As starting materials a high bituminous coal and a semianthracite were used. Active carbons with a wide range of textural properties were obtained. Materials with specific surface areas varying from 120 to 1300 m(2) g(-1) can be produced with the correct choice of experimental conditions. From the results, general guidelines may be established for the design of activated carbons with a particular porous network.