Bioassay-guided fractionation of a MeOH extract of the whole plant of Aceriphyllum rossii (Saxifragaceae) led to the isolation of two new triterpenes, 3alpha,23-isopropylidenedioxyolean-12-en-27-oic acid (1) and 23-hydroxy-3-oxoolean-12-en-27-oic acid (2), together with six known triterpenes, 3-oxoolean-12-en-27-oic acid (3), 3alpha-hydroxyolean-12-en-27-oic acid (4), beta-peltoboykinolic acid (5), aceriphyllic acid A (6), oleanolic acid (7), and gypsogenic acid (8). The structures of these compounds were elucidated on the basis of physicochemical and spectroscopic analyses. These compounds were evaluated for in vitro cytotoxicity against the K562 and HL-60 cell lines. Olean-12-en-27-oic acid derivatives (1-6) exhibited considerable cytotoxicity against K562 and HL-60 cell lines with IC(50) values ranging from 12.2 to 28.7 microM and from 12.1 to 25.8 microM, respectively.