Four new diterpenes ( 1- 4) were isolated from the soft coral Xenia elongata using a novel cell-based screen for apoptosis-inducing, potential anticancer compounds. The molecular structures of the diterpenes were determined using a combination of NMR and mass spectrometry. The bioactivities were confirmed using a specific apoptosis induction assay based on genetically engineered mammalian lines with differential, defined capacities for apoptosis. The diterpenes induce apoptosis in micromolar concentrations. This is the first report of apoptosis induction by marine diterpenes in xenicane skeletons.