Jacaranda mimosifolia Linn. seeds yielded a water soluble polysaccharide on acid hydrolysis as D-galactose and D-mannose in 2:7 molar ratio. Upon periodate oxidation of seed polysaccharide with sodium metaperiodate, it consumed 2.30 moles of periodate with simultaneous liberation of 1.05 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.