Two new diterpene compounds have been isolate from the roots of Eragrostis ferruginea (Thunb.) Beauv. and their structures were elucidated as isopimara-9(11), 15-0ien-l9-ol-3-one and cassa-13(14), 15-diene-3, 12-dione by various spectroscopic me-thods. We have also isolated a known diterpene diol isopimara-9(11). 15-diene-3β, 19-dio1