Two evolved gas analysis techniques were used to study modified single-wall carbon nanotubes (SWNTs). These techniques were thermogravimetry-mass spectrometry (TG-MS) and pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS). Increased weight loss was exhibited in the modified SWNTs below 800°C, which was attributed to the addition of methoxide introduced during the modification. The localized environments of the SWNT provide bonding sites of varying strength that results in the staged evolution of the methoxide masses. The continued evolution of methoxide related masses is a result of the variations in the localized environments of the SWNTs, including the curved ends and various other possible sites along the sidewalls. However, once all the modifications have been removed, the overall structure of the SWNT still remains as intact as the pristine sample as indicated by the slope of the weight loss at higher temperatures.