We describe an efficient and novel route to graft covalently polystyrene (PS) on the external layers of nitrogen-doped multi-walled carbon nanotubes (CNx MWNTs) using atomic transfer radical polymerization (ATRP). The doped tubes did not require any acid treatment prior to the ATRP reaction. Samples were characterized using FTIR, thermogravimetric analyses, high resolution transmission microscopy, electron energy loss spectroscopy, energy dispersive X-ray spectroscopy, and gas chromatography/mass spectrometry (GC-MS). All the tubes were coated with a uniform layer of PS (3-5 nm thick). These grafted tubes could behave as efficient fillers in the manufacture of reinforced polymers exhibiting outstanding mechanical properties. (c) 2005 Elsevier B.V. All rights reserved.