In the present paper, some of our work on Al2O3-SiO2/Al2O3- and Ti-pillared smectites is discussed mainly from the point of hydrothermal stability and cracking performance. Some initial results of a study on pillaring of regularly and randomly interstratified illite montmorillonite mixed layer clays are also included. One type of materials studied, i.e. alumina-montmorillonites, may be attractives alternatives to the active matrices, often alumina, currently used in FCC-catalysts designed for cracking of heavy oils.