Single tip tungsten emitters, nanocrystalline graphite (NCG) emitters, gated silicon field emitter arrays, thoriated tungsten filament emitters, and micromachined n-type polycrystalline silicon thermionic emitters were investigated as potential electron sources for miniature x-ray devices. The emission sources were characterized in a demountable 3.5 mm diameter Schott glass 8250 tube using a 45degrees cone angle, 1 mm diameter tungsten anode. X-ray characterization was performed in a custom-built shielded system, surrounding the tube using an AMPTEX, model XR-100T-cadmium zinc telluride crystal detector. The best results in terms of reliability and recovery from flashover events were obtained with the NCG emitter. Lateral, distal, and rotational x-ray spectra were obtained for the NCG emitter. Initial integration efforts of mounting the x-ray source on the end of a cardiac catheter yielded 15 W standoff voltages for a 0.2 mm catheter wall thickness. (C) 2003 American Vacuum Society.