Two new cytotoxic cembranoid diterpenes, brassicolide (1) and brassicolide acetate (2); a new cytotoxic sesquiterpene, (-)-4alpha-O-acetyl-selin-11-en (3); and six cytotoxic terpenoids, (-)-selin-11-en-4alpha-ol (4), 2-hydroxynephthenol (5), nephthenol (6), cembrene A (7), epoxycembrene A (8), and (-)-beta-elemene (9), have been isolated from the Formosan soft coral Nephthea brassica. The structures of compounds 1-9 were determined by spectral, chemical, and X-ray crystallographic analysis.