Carbon nanotubes are good candidates for electron field- and photo-emitters at the nanoscale since their sharp geometries lead to significant external field enhancement. Also, their mechanical strength and structural completeness alleviate issues related to stability and lifetime that may be present in small-scale emitters that have loose atoms at their tips. Here, we demonstrate how an external electron beam can stimulate electron emission from the tip of a nanotube that is lying on an insulating surface and is subject to an external electric field, thus making it act as an electron bombardment source. (C) 2004 American Vacuum Society.