Triterpene-oligoglycoside constituents of Astragali Radix, the root of Korean Astragalus membranaceus BUNGE (Leguminosae), were isolated. By means of enzymatic and chemical degradations, the 9, 19-cyclolanostane-type triterpene named cycloastragenol (1), which was the common genuine aglycone of ten of eleven astragalosides, and the lanost-9 (II)-ene-type counterpart named astragenol (5), which was an artifact aglycone secondarily formed from 1, were isolated. On the basis of chemical and physicochemical evidence, the structures of cycloastragenol and astragenol were elucidated as (20R, 24S)-3β, 6α, 16β, 25-tetrahydroxy-20, 24-epoxy-9, 19-cyclolanostane (1) and (20R, 24S)-3β, 6α, 16β, 25-tetrahydroxy-20, 24-epoxy-lanost-9 (11)-ene (5), respectively.