Alcohol-insoluble residues (AIRs) from Festuca and Zea cell cultures contained 7.4 and 35 nmol esterified ferulate mg −1, respectively. Driselase solubilised 79% of the feruloylated material from both AIRs. Of the feruloyl esters solubilised from Festuca and Zea AIRs, 72 and 56% respectively were small enough to be mobile on paper chromatography. The major feruloylated product of Zea AIR was the known 5- O-feruloyl-α- l-Ara f-(1 → 3)-β- d-Xyl p-(1 → 4)- d-Xyl (Fer-Ara-Xyl-Xyl). In contrast, the smallest major feruloylated product of Festuca AIR was a feruloyl pentasaccharide ( 3) containing 3 Xyl, 1 Ara and 1 non-pentose residue (NPR). The Ara and two of the three Xyl groups of 3 were resistant to NaIO 4. Mild acid hydrolysis of 3 gave xylobiose, a feruloyl trisaccharide and β- d-Xyl p-(1 → 2)-(5- O- feruloyl)- l-Ara. Compound 3 was therefore NPR-(1 → 3)-β- d-Xyl p-(1 → 2)-(5- O-feruloyl)-β- l--Ara f-(1 → 3)-β- d-Xyl p-(1 → 4)- d-Xyl. We conclude that the complex feruloyl oligosaccharide side-chains of Festuca arabinoxylan do not protect the polysaccharide against hydrolysis by the fungal glycanases present in Driselase. © 1997 Elsevier Science Ltd. All rights reserved