Abstract: Catalytic conversion of a hydrocarbon feedstock comprising a stage of catalytic cracking of a hydrocarbon feedstock, a stage of separation of the products of cracking from the catalytic mass, and a stage of regeneration and recycling of the catalytic mass and between the stage of regeneration of the catalytic mass and the stage of separation of the products of cracking there is injected continuously or intermittently, at one or more points, in admixture with at least one hydrocarbon to be treated, at least one diorganophosphite of the general formula ##STR1## where R.sub.1 and R.sub.2, which may be alike or different, are selected from the group consisting of alkyl, aryl or aralkyl groups having from 1 to 30 carbon atoms.