The nucleophilic substitution of chlorobenzene with ammonia, leading to aniline, was investigated over various copper-exchanged catalysts using vapour-phase reactants. Benzene and diphenylamine were formed as side-products. The zeolites tested (Cu-L, Cu-mordenite, Cu-Y, Cu-ZSM-5, and Cu-beta) gave better results than copper-containing silica-alumina, because of the high deactivation rate of the latter. On zeolites Cu-L, Cu-mordenite, and Cu-ZSM-5, substitution prevailed : with Cu-mordenite and Cu-ZSM-5, aniline selectivities of 90-94% were obtained. In contrast, reduction towards benzene was pronounced on Cu-beta and especially on Cu-Y. In more detailed studies with Cu-mordenite, two deactivation regimes were observed, related to the reaction temperature. With Cu-L, the dehalogenation towards benzene was investigated : it is ascribed to copper reduction, followed by the reduction of chlorobenzene with the copper(0) particles thus obtained.