Activation upon cyclic oxygen chemisorption-desorption has proved to be an efficient way to develop porosity at low burn off from waste tires char. In this work the influence of particle size, desorption temperature, and the number of cycles is studied. Highest values of burnoff and specific surface area (S-BET) are obtained for the largest particle diameter (3 mm average) and at intermediate desorption temperature (650 degrees C). In these conditions S-BET values around 500 m(2)/g can be achieved at burnoffs of about 30%, and close to 600 m(2)/g at around 45% burnoff, with a mean pore size of 10 nm and a micropore volume close to 0.08 cm(3)/g. Although the surface area is moderate, the low burnoff and high S-BET/burnoff ratio achieved make it possible to maintain initial granular morphology of the particles even after 20 cycles of activation.