Near-infrared ( NIR ) reflectance spectrophotometry has been successfully used for rapid, efficient identification of carboxylated cellulose in whole (nondisintegrated) linen textile samples subjected to a thermal treatment in the presence of high CO and CO2 concentrations. Mass spectrometric analysis of enzymatic hydrolysates of the treated textiles demonstrates the existence of carboxylated D-glucose residues produced by this procedure. Near-infrared spectrophotometry proves to be an accurate and simple approach to fast identification and characterization of these carboxylated cel lulose derivatives in whole textile samples.