Hydrothermal liquefaction of rice straw was performed at temperatures from 280 to 320 degrees C under different reaction environments viz., N-2, O-2 and CO2. N-2 and CO2 did not show any significant change in the product distribution, however, in case of liquefaction using O-2, the bio-oil yield was very low. Maximum bio-oil yield (17 wt%) as well as conversion (78%) was observed in case of liquefaction using N-2. TOC analysis indicated that the maximum organic carbon conversion (77%) was under N-2 environment. Ether soluble bio-oil obtained under O-2 environment showed higher aliphatic proton content than N-2 and CO2, whereas, aromatic proton content was higher in case of N-2 and CO2 than O-2. H-1 and C-13 NMR showed that bio-oil obtained at all the conditions was highly aliphatic and aromatic in nature. GC/MS showed that bio-oil (ether and acetone soluble) obtained under different reaction conditions was composed of phenol, guaiacol, catechol, syringol and their derivatives. (C) 2015 Elsevier B.V. All rights reserved.