Four new euphane-type triterpenes, kansenone (1), kansenonol (3), 11-oxo-kansenonol (4), kansenol (5), and a new tirucallane-type triterpene, epi-kansenone (2), were isolated from a 60% EtOH extract of Euphorbia kansui, together with alpha-euphol. Their structures were elucidated on the basis of extensive analysis of their 1D and 2D NMR spectral data. This appears to be the first report of the natural occurrence of euphane/tirucallane-type triterpenes with a ketone at C-7. In vitro treatment of cultured individual Xenopus laevis cells at the blastular stage with 1-4 significantly arrested cleavage of the cells (10 microg/mL of each compound resulted in >50% cleavage arrest).