Pretreatment of rice straw on pilot scale steam explosion has been attempted to achieve maximum sugar recovery. Three different reaction media viz. water, sulfuric acid and phosphoric acid (0.5%, w/w) were explored for pretreatment by varying operating temperature (160, 180 and 200 degrees C) and reaction time (5 and 10 min). Using water and 0.5% SA showed almost similar sugar recovery (similar to 87%) at 200 and 180 degrees C respectively. However, detailed studies showed that the former caused higher production of oligomeric sugars (13.56 g/L) than the later (3.34 g/L). Monomeric sugar, followed the reverse trend (7.83 and 11.62 g/L respectively). Higher oligomers have a pronounced effect in reducing enzymatic sugar yield as observed in case of water. Mass balance studies for water and SA assisted SE gave total saccharification yield as 81.8% and 77.1% respectively. However, techno-economical viability will have a trade-off between these advantages and disadvantages offered by the pretreatment medium. (C) 2014 Elsevier Ltd. All rights reserved.