Triterpenoid saponins, impatienosides A-G, together with 12 known saponins, were isolated from the whole plants of Impatiens siculifer. Their structures were established on the basis of extensive 1D and 2D NMR and MS analyses coupled with chemical degradation. Cytotoxic activities of the isolated saponins were evaluated against three human cancer cell lines: human myeloid leukemia HL-60 cells, human stomach KATO-III adenocarcinoma, and human lung A549 adenocarcinoma.