In this Letter, we present an in situ Raman spectroscopy study of oxidation-induced changes in the structure and composition of double-wall carbon nanotubes (DWCNTs). Above 480 degreesC, the intensity of the D band decreases to less than 0.01% of the G band intensity, when measured using the 780 nm laser excitation. The D band was absent from the Raman spectra recorded with the 514.5 nm excitation. Thermogravimetric analysis and high-resolution transmission electron microscopy are used to explain the observed results. We conclude that oxidation provides a purification method for the DWCNT which leads to a sample containing tubes having nearly clean surfaces without disordered carbon. (C) 2004 Elsevier B.V. All rights reserved.