In a process for reducing the level of tert-butylbenzene in a mixed butylbenzene feed comprising tert-butylbenzene and sec-butylbenzene, the feed is contacted under dealkylation conditions with a catalyst system comprising a dealkylation catalyst whereby the tert-butylbenzene is selectively dealkylated to produce an effluent stream which comprises benzene and which has a lower concentration of tert-butylbenzene than said feed.