Bioassay-directed fractionation of ethanol extracts of the roots and leaves of the plant Cassipourea madagascariensis resulted in the isolation of the two new terpenoids cassipourol (1) and cassipouryl acetate (2) in addition to the three known compounds, 3beta,30-dihydroxylup-20(29)-ene (3), 30-hydroxylup-20(29)-en-3-one (4), and combretol (5). The structures of the two new compounds were established on the basis of 1D and 2D NMR spectroscopic data and chemical conversion. All the isolated compounds were tested against the A2780 human ovarian cancer cell line; the two diterpenes (1 and 2) showed moderate cytotoxic activity, while the three known compounds (3-5) were weakly active.