The present study was designed to solubilize/hydrolyze lignocellulosic biomass of kenaf stems in subcritical water, in an environmentally friendly manner. The hydrolysis efficiency was examined with respect to several parameters such as sonication of biomass-water mixture before thermal treatment, changing temperature and pressure of the hydrolysis process, adding carbon dioxide or nitrogen as pressurizing gas. The molar mass of polysaccharide fractions in the sonication pretreated solutions notably decreased because of effective degradation. The extent of hydrolysis was more effective at higher temperatures and under carbon dioxide atmosphere rather than nitrogen as the pressurizing gas. In comparison to untreated sample, 200 degrees C-subcritical water-treated kenaf stems had significant morphological and structural changes on plant cell wall surface that was further distorted at 250 degrees C. (C) 2010 Elsevier Ltd. All rights reserved.