Chemical investigation of the tubers of Dioscorea polygonoides has resulted in the isolation of a novel polyoxygenated spirostanol saponin, named diospolysaponin A (1), along with a known spirostanol saponin (2).The structure of 1 was determined on the basis of spectroscopic analysis and by enzymatic hydrolysis followed by chromatographic and spectroscopic studies to be (23S,25R)-12a,14a,17a,23-tetrahydroxyspirost-5-en-3b-yl O-a-L-rhamnopyranosyl-(1AE2)-b-D-glucopyranoside.The cytotoxic activity of 1 and 2 and their aglycons against HSC-2 cells is briefly presented.