The structure of one hemicellulose A fraction (A-1) isolated from grape skins ( Vitis vinifera) of the Palomino variety has been studied by methylation analysis, NMR spectroscopy and partial acid hydrolysis. Hemicellulose A-1 appeared to be homogeneous with a weight-average M r of 35 544. It was shown to be a linear acidic xyloglucan constituted by a linear chain of xylopyranosyl and glucopyranosyl residues linked by β-(1 → 4) glycosidic bonds containing 4- O-methylglucuronopyranosy acid, l-arabinofuranosyl and xylopyranosyl residues attached at position 2, in a ratio of one residue for every 10 units of xylose in the main chain, and l-arabinofuranosyl and glucopyranosyl residues attached at position 6 of the units of glucose, in a ratio of one residue for every four glucoses in the main chain.