Acetic acid-catalyzed hydrothermal pretreatment was done on corn stover under 195 degrees C, 15 min with the acetic acid ranging from 5 x 10(-3) to 0.2 g g(-1) corn stover. After pretreatment, the water-insoluble solids (WISs) and liquors were collected respectively. Arabinan recoveries from both WIS and liquors were investigated. The results indicate that there was no detectable arabinan left in the WIS when the acetic acid of 0.1 and 0.2 g g(-1) corn stover were used in the pretreatment. The arabinan contents in the other WISs were not more than 10%. However, the arabinan found in the liquors was not covering the amount of arabinan released from the raw corn stover. For the arabinan recovery from liquor fractions, the highest of 43.57% was obtained by the pretreatment of acetic acid of 0.01 gg(-1) of corn stover and the lowest was only 26.77% when the acetic acid of 0.2 g g(-1) corn stover was used. As far as the total arabinan recovery, the pretreatment with acetic acid at 0.01 g g(-1) raw corn stover yielded the highest and it was 52.16%. This meant that almost half of the arabinose was degraded during the pretreatment process. (C) 2009 Elsevier Ltd. All rights reserved.