In the study on the chemical constituents from the Formosan marine organisms, four steroids, including three cholanic acid type metabolites, deoxycholic acid 3,12-diacetate (1), deoxycholic acid 3,12-diacetate-24-methyl ester (2), 3£\,7£\,12£\-triacetoxy-5£]-cholanic acid (3), and a principal steroid, gorgosterol (4), were isolated from the soft coral Klyxum simplex, collected at southern Taiwan coast. The structures of steroids 1-4, were elucidated by extensive spectroscopic methods, particularly in 1D and 2D NMR experiments. To best of our knowledge, there is no report on the isolation of cholanic acid type steroids from any marine source. Based on detailed analysis, steroid 2 was found to be a new natural product and this is the first time to isolate steroid 1 from natural resource. Furthermore, two known isoquinoline quinones, mimosamycin (5) and O-demethylrenierone (6) and a known steroid,24,28-didehydroaplysterol (7), were obtained from an Indonesian sponge belonging to the genus Halichondria (Halichondriidae). The structures of metabolites 5-7 were determined by spectral data analysis and by comparison with the spectral and physical data of other known compounds. The antimicrobial activity of compounds 1-7 against Staphylococcus aureus were assayed. It was found that compounds 1, 5 and 6 showed antimicr- obical activity toward Staphylococcus aureus.