A field ionization source based on densely spaced, vertically aligned carbon nanotubes (CNTs) has been developed and evaluated. The CNTs contained nickel particles at their tips. This source would be suitable for analytical mass spectrometry. With a positive voltage on the dense CNT arrays, the strong electric field generated around the CNT tips has effected field ionization. The ionization of inert gases, including helium, and organic compounds, including acetone and methane, and the control and the transfer of the resulting ions have been achieved. These results represent a base for application of this new ion source in mass spectrometry. (C) 2011 Elsevier B.V. All rights reserved.