The critical dose for graphitization of diamond as a result of ion implantation induced damage (boron and arsenic) and subsequent thermal annealing is determined by combining secondary ion mass spectroscopy measurements, chemical etching of the graphitized layer, and T R I M simulations. Li ions are implanted as a deep marker to accurately determine the position of the graphite/diamond interface. The damage density threshold, beyond which graphitization occurs upon annealing, is found to be 1022 vacancies/cm3. This value is checked against published data and is shown to be of general nature, independent of ion species or implantation energy.