Diamond based electronic devices promise to exhibit unique properties. In order to realize devices diamond has to be doped to render it electrically conductive. In the present work the doping of diamond and of polycrystalline CVD diamond films are reviewd with particular emphasis to ion-implantation doping and to attempts to dope diamond by in-diffusion of the dopants. The quest for finding ways to obtain n-type conductivity in diamond will be critically examined.