We have developed high-current density field emission sources using arrays of multiwalled carbon nanotube bundles. The field emission behavior of a variety of lithographically patterned array geometries was investigated and the arrays of 1-mum and 2-mum-diameter nanotube bundles spaced 5 Am apart (edge-to-edge spacing) were identified as the most optimum combination, routinely producing 1.5-1.8 A/cm(2) at low electric fields of approximately 4 V/mum, rising to >6A/cm(2) at 20 V/mum over a similar to100-mum-diameter area. We have found that the field emission performance depends strongly on the bundle diameter and interbundle spacing and such arrays perform significantly better in field emission than ordered arrays of isolated nanotubes or dense, continuous mats of nanotubes previously reported in literature. (C) 2005 American Vacuum Society.