Aromatic amines, for example, diarylamines such as diphenylamine, dinaphthylamine, N-phenyl-N-naphthyl amine etc., are alkylated by passing a mixture of the amine and an olefin, though a clay catalyst in a fixed bed reactor system. The process is conveniently run as a continued process, produces an alkylated aromatic amine in excellent purity and provides efficiencies in material and energy use.