The effects of high severity operation and ZSM-5 addition on the FCC product yield distribution have been studied in a down-flow reactor unit. VGO cracking at high reaction temperatures of 500-650 degrees C increases the yield of light olefins (propylene and butenes) with a corresponding loss in gasoline yield and increase in dry gas formation. Similar behavior is observed with the addition of 0-20 wt % ZSM-5 additive, however, with no increase in dry gas. The combination of the two effects (high severity and ZSM-5 addition) makes the FCC unit an excellent source of light olefins for downstream petrochemical and alkylation units. The novel process configuration increased the light olefin yield without significant loss in gasoline by suppressing thermal cracking reactions and dry gas formation.