Abstract: The invention described is concerned with atomizing an oil fraction of crude oil to provide a fog of oil droplets in diluent gaseous material which is sprayed into an upwardly flowing annular dense mass of catalyst particles to form a high temperature suspension therewith and conveyed through a riser conversion zone under selected hydrocarbon conversion conditions suitable for cracking the oil droplets to gasoline and light cycle oil boiling range products. The oil feed preparation and distribution arrangement to form a suspension with catalyst particles of desired elevated temperature is employed in combination with a two-stage catalyst regeneration operation designed and operated to achieve catalyst temperatures at least equal to the pseudo-critical temperature of the oil feed and at least above the end boiling point of gas oil boiling range material and resid product of vacuum distillation.