Impure hexamethylenediamines and more particularly those hexamethylenediamines containing contaminating amounts of tetrahydroazepine (THA), or more generally contaminating amounts of imines, are purified by distillation carried out with a short retention time of the impure hexamethylenediamine in the distillation column; the hexamethylenediamine obtained has a very low concentration of THA.