Quercus incana Roxb. seeds yielded a alkali soluble polysaccharide on acid hydrolysis as D-galactose and D-mannose in 1:5 molar ratio. Upon periodate oxidation with sodium metaperiodate, the seeds polysaccharide consumed 1.24 moles of periodate with simultaneous liberation of 0.102 moles of formic acid per mole of anhydroglucose unit. On the basis of methylation results the proposed polysaccharide structure has been confirmed by periodate oxidation method.