From the ethanol extract of the Chinese traditional medicine, rhizomes of Polygonatum odoratum, a new steroidal saponin POD-II together with beta-sitosterol and its glucoside, and three known saponins were isolated. On the basis of chemical evidence and spectral analysis (UV, IR, EI-MS, 1HNMR and 13CNMR), the structure of POD-II was elucidated as 3-O-beta-D-glucopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta-D- glucopyranosyl-(1-->4)-galactopyranosyl-25(R)-spirost-5-en-3 beta,14 alpha-diol. Preliminary pharmacological tests showed that POD-II could induce the colony stimulating factor (CSF) in mouse serum; and POD-III, at the concentration of 0.1 microgram.ml-1 was shown to synergize the suboptimal and optimal concentration of Con A and lipopolysaccharide to stimulate lymphocytes proliferation.