Abstract The n-hexane extract of Formosan gorgonian coral Isis hippuris (Isididae) collected from Green Island was found to exhibit significant cytotoxicity against P-388, A-549 and HT-29 cell lines. Cytotocicity-guided fractionation of this extract led to isolation of a known subersenone (1), five new suberosanane analogues, suberosanone (2), suberosenol A (3), suberosenol B (4), suberosenal A acetate (5) and suberosenol B acetate (6), two sesquiterpenes of novel skeletons, isishippuric acid A (7) and B (8). Three known compounds, subergorgic acid (9). 3-hexadecyl-5-hydroxy- 5-methyl-5-hydrofuran-2-one (10) and prenga-1,4-diene-3,20-dione (11) were also isolated along with the novel compound. Compounds 2-6 and 8 showed potent cytotoxicities against P-388, A-549 and HT-29 cells.