To develop a microfocused x-ray source, field emission properties of a bundle of multiwalled carbon nanotubes were investigated under an ordinary vacuum pressure of 5 x 10(-7) Torr for a practical use. Total emission current reached up to 1.3 mA at an applied voltage of -7 kV. An emitted electron beam was focused on a Cu anode by using a simple electrostatic lens and excited an x ray with the source size of less than 30 mu m. X-ray transmission images were taken as a preliminary demonstration for a microfocused x-ray source and clear images whose resolutions were nearly equal to the source size of x ray were easily obtained. (c) 2006 American Vacuum Society.