A process for the production of high octane number gasoline from light refinery olefins and benzene-containing aromatic streams such as reformate. Light olefins including ethylene and propylene are extracted from refinery off-gases, typically from the catalytic cracking unit, into a light aromatic stream such as reformate containing benzene and other single ring aromatic compounds which is then reacted with the light olefins to form a gasoline boiling range product containing akylaromatics. The alkylation reaction is carried out in the liquid phase with a catalyst which preferably comprises a member of the MWW family of zeolites such as MCM-22 using a fixed catalyst bed.