5-Membered, 6-membered or 7-membered cyclic imines are prepared by hydrogenating a C.sub.2 -C.sub.4 -alkanedinitrile in the liquid phase, at from 180.degree. to 300.degree. C. and under superatmospheric pressure, in the presence of a catalyst, by a process in which an iron catalyst obtained by reduction of an iron oxide with hydrogen at .ltoreq.500.degree. C. is used.