Abstract
A review is given of fundamental processes leading to the production of multicharged ions by electron-atom collision : direct electron ejection, Auger process, electron shake-off. Results concerning ionization crosssections by electron impact are discussed. Some approximate methods allowing to a good knowledge of the ionic population in different types of ion sources (hot plasma devices, laser ion source, electron bombardment and discharge sources). At the end, some problems concerning emittance and brightness of heavy multicharged ion sources are examined.