A steroidal saponin, named tuberoside, together with seven known compounds, were isolated from the seeds of Allium tuberosum Rottl. ex Spreng. Its structure was established by spectroscopic data, hydrolysis, and comparison with spectral data of known compounds to be (2a, 3b, 5a,25S)-2,3,27-trihydroxyspirostane 3-O-a-l-rhamnopyranoyl-(1!2)-O-[a-l-rhamnopyranoyl-(1!4)] b-d-glucopyranoside.