The methylene chloride and acetone extracts of Formosan soft coral Clavularia violacea (Collected at Green Island) were found to exhibit significant cytotoxicity against P-388, A-549 and HT-29 cancer cell lines. Chromatographic separation let to the isolation of one prostanoid, 1, two cembranoid deterpenes, 2 and 3, one aromadedrane-type sesquiterpene, 4, one neodollabellane diterpene, 5, (+)-curcuphenol, 6 and two sesquiterpene lactones, 7 and 8. Compounds 1, 2, 4, and were new compounds. Compounds 1-5 exhibited significant cytotoxicity against P-388, HT-29 and A-549 cancer cell.