Chemical investigation of the two soft corals Nephthea sp. and Sarcophyton cherbonnieri, collected from the Fiji Islands and the Great Barrier Reef, respectively, led to the isolation of three new furano-cembranoids (1-3), two seco-cembranoid acetates (5, 6), along with the known compounds sarcoglaucol (4) and decaryiol (7). The structures of the new compounds were elucidated by employing spectroscopic techniques (NMR, MS, UV, IR and CD). Seco-cembranoids are extremely rare structures. Compounds 1, 3, and 7 were found to be cytotoxic towards several tumor cell lines (GI50 values ranged from 0.15 to 8.6 micrograms mL-1). Compound 7 arrests the cell cycle in the G2/M phase.