Structural characteristics of lignocellulosic biomass such as surface area, pore volume, crystallinity, hemicellulose, and lignin content significantly affect the yield of fermentable sugars for bioethanol production. In the present work, the effect of dilute acid pretreatment was studied on structural characteristics of wheat straw, using different combinations of process variables (temperature, time, and acid concentration). Pretreated wheat straw (PWS) exhibited higher available surface area and pore volume along with low hemicellulose and lignin content. Crystallinity index (CrI) of biomass at different pretreatment conditions showed an increased trend followed by sharp decrease at high temperature (190 degrees C) conditions. Maximum increase in surface area (7.1m(2)/g compared to 4.0m(2)/g for untreated wheat straw) was obtained at pretreatment conditions of 180 degrees C temperature, 0.5% (v/v) acid, and 7min time. SEM imaging of biomass revealed that pore breaking, compression of pores, and partial pore blocking in the case of high temperature (190 degrees C) pretreatment conditions may be the reason behind decreased surface area of biomass. FT-IR analysis showed almost complete hemicellulose removal and acid-soluble lignin removal after dilute acid pretreatment but insufficient removal of acid insoluble lignin. [Supplementary material is available for this article. Go to the publisher's online edition of Chemical Engineering Communications for the following free supplemental resource: figure showing XRD pattern of biomass with respect to different pretreatment conditions.]