Electroluminescence in the visible region is observed when AlN is excited by either ac or dc. The emitted spectra consist of narrow bands in the 400-500 m\ensuremath{\mu} region and broad continuous bands in the 500-700 m\ensuremath{\mu} region. The broad bands vary according to the activator agents. With ac, the luminescence is in phase with the applied voltage. With dc, light is emitted in the vicinity of the cathode and decays with time. This decay can be explained by polarization. The presence of a barrier at the cathode is indicated. Impact excitation is proposed.