To estimate the contribution of all major components to the thermal properties of natural hemp fiber bundles, the thermal decomposition of hemp fibers following several chemical treatments was Studied by the differential thermogravimetric analysis (DTA/TGA). Contrary to what was observed with measurements conducted under air, the thermal degradation of all major hemp fiber components (pectins, hemicellulose, cellulose, and lignin principally) could be easily detected and deconvoluted under inert atmosphere. The intensity of the TGA peaks observed at 235 degrees C (characteristics of pectin) and at 265 degrees C (characteristics of hemicellulose) decreased after all fiber chemical treatments. This resulted in an overall increase of the cellulose percentage. Based on the onset temperature of DTA, it was found that the thermal stability decreased in the following order: NaOH-treated fibers, silane-treated fibers, Solvent extracted fibers (water/ethanol mixture, 20/80 v/v), and untreated hemp fibers. Moreover, the difference of the mass loss (%.) between TGA under argon of silane-treated fibers and untreated fibers showed that some silane molecules were chemically attached to hemp fiber bundles. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 112: 226-234, 2009