From the underground parts of Ruscus aculeatus, a new bisdesmosidic spirostanol saponin named aculeosides B (2) was isolated, and its structure was determined on the basis of spectroscopic analysis, including 2D NMR techniques. Aculeoside A (1), which was previously isolated from the same plant source, exhibited inhibitory activity on cell growth of leukemia HL-60 cells with an IC50 value of 0.48 microgram mL(-1), while aculeoside B (2) was inactive.