Natural products have historically been a rich source of "lead compounds" for drug discovery. Although started only fifty years ago, the investigation of marine organisms aimed at searching new biologically active compounds has now gained a recognized role in this kind of studies. My research work, carried out in the frame of the book program, has been addressed at this research field and, in particular, at the isolation and identification of bioactive constituents from Egyptian Marine Soft Corals. This investigation resulted in the isolation of six new compounds, belonging to different structural classes, some of which possessing interesting anti cancer activity. The structures of all new compounds were elucidated using modern spectroscopic methods including 1D, 2D NMR, X-ray and FAB-MS. Part one: Sarcophyton glaucum Chemical analysis of the less polar fractions of the organic extract obtained from Sarcophyton glaucum afforded three new compounds (1-3). Part two: Sarcophyton Trocheliophorum. Chemical investigation of the soft coral has led to the isolation of six cembranoids, two of which are new, Trochelioid A (1) and B (2), and one, 16-oxosarcophytonin E(3).