Abstract: The invention relates to a method and apparatus for injecting and conditioning regenerated catalyst particles at the base of a catalytic cracking reactor/elevator below the zone where the feedstock to be cracked is injected to give better uniformity of treatment and control of the effective C/O ratio. A first fluid is injected at a low rate into the reactor below the level where the catalyst particles coming from the regenerator are introduced so as to form a dense phase fluidized bed, and a second fluid is injected at a higher rate substantially above the zone where the catalyst particles coming from the regenerator enter so as to form a homogenized dilute phase fluidized bed of catalyst prior to subsequent contact with the feedstock to be treated.