In a hydrocarbon upgrading process, a hydrocarbon feed is treated in at least one of a steam cracker, catalytic cracker, coker, hydrocracker, and reformer under suitable conditions to produce a first stream comprising olefinic and aromatic hydrocarbons. A second stream composed mainly of C4 to C12 olefinic and aromatic hydrocarbons is recovered from the first stream and at least part of the second stream is contacted with a catalyst in the absence of added hydrogen under reaction conditions including a temperature of about 450° C. to about 70° C. effective to dealkylate, transalkylate, crack and aromatize components of the second stream to produce a third stream having an increased benzene and/or toluene content compared with the second stream and a C3− olefin by-product. The C3− olefin by-product and a fourth stream comprising toluene are then recovered from the third stream.