Abstract: In the catalytic cracking of oil, especially in a riser-type of transport pipe reactor, feedstock in the liquid state is added to the reactor together with sufficient regenerated catalyst to effect essentially complete vaporization of the oil but with minimum cracking. Preferably the regenerated catalyst is cooled to about 900.degree. to 1100.degree. F prior to contact with the oil. The mixture of oil and catalyst is propelled through the riser until the oil is substantially vaporized and then a major portion of hot regenerated catalyst is added to effect the cracking reaction.