Three natural cembranoids from the Red Sea soft coral Sarcophyton glaucum namely sarcophine (1), (+)-7alpha,8beta-dihydroxydeepoxysarcophine (2) and sarcophytolide (3) were evaluated for their potential inhibitory effects on growth of mouse melanoma B16F10 cells. Compounds (1) and (2) maximally inhibit viability of melanoma cells during 48 hr and 72 hr treatment at concentrations that show no cytotoxicity on monkey kidney CV-1 cells and also inhibit de novo DNA synthesis and PARP activity. Compound (3) produced cytotoxic effects at the same concentration range it produces its antitumor effects. These data suggest that (1) and (2), but not (3), have potential for further development as antitumor agents against melanoma.