The nitrogen-incorporated multiwalled carbon nanotubes (N-MWCNTs) were synthesized by dc plasma-enhanced chemical vapor deposition with a gas mixture Of C2H2, NH3, and N-2. Nitrogens in the N-MWCNTs were pyridinic nitrogen and graphitic nitrogen. With increase in the flow rate of N2 gas during the synthesis of MWCNTs, the pyridinic nitrogen increased much more than graphitic nitrogen. The near-edge x-ray absorption fine structure spectra revealed that the density of states such as pi*, sigma*, and pi* + sigma* bands of the N-MWCNTs decreased with increase of concentration of pyridinic nitrogen incorporated in the MWCNTs. The intensity ratio of the D band to the G band of Raman spectrum increased with the incorporation of nitrogen into MWCNTs. (c) 2005 American Vacuum Society.