From rhizomes and roots of Panax vietnamensis HA et GRUSHV., Araliaceae, commonly known as Vietnamese Ginseng, two new acetylated saponins named vina-ginsenoside-R1 (13) and vina-ginsenoside-R2 (15) were isolated. On the basis of chemical and spectral data, 13 was formulated as monoacetyl 24(S)-pseudo-ginsenoside-F₁₁ and 15 was proved to be monoacetyl majonoside-R2.Besides the two new saponins and β-sitosteryl-3-O-β-D-glucopyranoside, sixteen known saponins were also isolated and identified. Dammarane saponins : ginsenoside-Rh₁ and 20(R)-ginsenoside-Rh₁ (1), ginsenosides-Rg₁ (2), -Re (3), -Rd(6), -Rb₃ (7), -Rb₂ (8), -Rb₁ (9), pseudo-ginsenoside-RS₁ (=monoacetyl ginsenoside-Re, 4), notoginsenosides-R1 (5) and -Fa (10). Ocotillol-type saponins : pseudo-ginsenoside-RT₄ (11), 24(S)-pseudo-ginsenoside-F₁₁ (12), majonosides-R1 (16) and -R2 (14). Oleanolic acid saponins : ginsenoside-Ro (=chikusetsusaponin V, 17) and hemsloside-Ma3 (18), a saponin previously isolated from a cucurbitaceous plant, Hemsleya macrosperma C. Y. WU.Despite having large horizontally elongated rhizomes, the underground part of this plant contains mainly dammarane saponins and a small amount of oleanolic acid saponins. In addition, the yield of ocotillol-type saponins, especially majonoside-R2, is surprisingly very high (more than 5% and ca. half of the total yield of saponin). This characteristic saponin composition has made Vietnamese Ginseng an interesting species among Panax spp.