The esterified hemicelluloses were prepared under homogeneous reaction conditions in the system N,N-dimethylformamide/lithium chloride by reacting the native hemicelluloses with various acyl chlorides (C-3-C-18) in the presence of 4-dimethylaminopyridine as a catalyst and triethylamine as a base within 30 min at 70-75 degrees C. The products obtained were characterized by means of Fourier transform IR chromatography, gel permeation chromatography, thermal analysis, and solubility. The degree of substitution of esterified hemicelluloses was controlled between 0.38 and 1.75 as a function of experimental conditions. Under an optimum reaction condition xylose unit/acyl chloride (molar ratio 1 : 3, tetraethylammonium % 160, 75 degrees C, 30 min), about 95% hydroxyl groups in native hemicelluloses were esterified. The molecular weight measurements showed a minimal degradation and hydrolysis of the products. The thermal stability of the products was also increased by modification.