A well-characterized saponite was intercalated with [Al13] polyoxo aluminium cations. Its surface area was studied by nitrogen and ethylene glycol adsorption : the relative validity of both techniques in the case of pillared clays was assessed and compared to the theoretically expected value. The structural stability was investigated both in high-temperature treatments and upon aging under air at room temperature. The catalytic properties for cracking of a heavy petroleum feedstock were compared with those of a commercial FCC catalyst and with results from the literature concerning similar systems. Pillared Al-saponites present several interesting properties : thermally stable porous structure and low coking. Their study seems promising in understanding the transformation of the pillars during calcination owing to the location of the aluminium only in the tetrahedral sheets.