Wheat straw was fractionated into cellulosic fibres, hemicellulose sugars and solid lignin oligomers through a two-stage, acid-catalyzed process. During the first stage, raw material was treated with dilute H2SO4 (0 . 5-2 . 5 N) at reflux temperature (99 . 5+/-1 . 0 degrees C) for 10-60 min. Subsequently, delignification was conducted with H2SO4 (2 N) in aqueous ethanol (62 . 5-87 . 5% EtOH v/v) at reflux temperature (81 . 0+/-2 . 0 degrees C) for 90 min. Selective hydrolysis of about 50% of the straw hemicelluloses (w/w on original straw hemicelluloses), converted to water-soluble oligo- and monosaccharides (first stage), followed by delignification in 87 . 5% v/v EtOH (second stage), led to optimal component fractionation efficiency with negligible cellulose loss (less than 2% w/w on original straw cellulose) and high lignin removal (more than 70% w/w on original straw lignin). By this two-stage process, high overall fibre yields (more than 60% on original raw material) and good pulp mechanical properties were achieved.