A process for preparing ethylbenzene from benzene and ethylene in which a vapor phase alkylation reactor is combined with a liquid phase transalkylation reactor wherein the xylenes content of the ethylbenzene product is less than 700 wppm. Also disclosed are ethylbenzene processes in which a series-arranged or combined vapor phase alkylation/transalkylation reaction zone is retrofitted to have a vapor phase alkylation reactor and a liquid phase transalkylation reactor, and in which a parallel-arranged vapor phase alkylation reactor and vapor phase transalkylation reactor is retrofitted to have a vapor phase alkylation reactor and liquid phase transalkylation reactor. An apparatus for the practice of the ethylbenzene process of this invention is disclosed.