The electron emission yields (&ggr;) from conductive (B doped) and undoped chemical vapor deposited diamond caused by light (protons) and heavy (argon) ion impact were measured as functions of ion dose and energy (40–300 keV). Very large values of &ggr; are obtained for the case of B doped diamond for both ions. Whereas the emission due to Ar is found to decay very rapidly towards the low &ggr; value measured for graphite, it remains persistently very high(&ggr;∼25)for the case of protons, indicating possible application of diamond as a sensitive detector for light ions. ©1998 American Institute of Physics.