Nitrogen-doped carbon nanotubes (CNx tubes) with nitrogen content of 7.6 at.% are synthesized on carbon papers. Thermal and chemical stability of the nanotubes are investigated by thermogravimetric anal- ysis, differential scanning calorimetry and X-ray pho- toelectron spectroscopy techniques. The results indicate that the nitrogen can be firmly kept in the nanotubes after annealing at 300 C in air. Under an argon atmosphere, the nitrogen would not release until 670 C, and half of the nitrogen incorporated is released after annealing at 700 C for 30 min. Chemical stability investigation indicates that the nitrogen incorporated in the nanotubes is very stable under the thermal and acid environment comparable to working condition of proton exchange membrane (PEM) fuel cells. Profile of the nitrogen species inside the nanotubes reveals that graphite-like nitrogen releases slower than any other kind of nitrogen in the nanotubes during the chemical stability measure- ment. These CNx tubes synthesized by this simple chemical vapor deposition method are expected to be