Five new halogenated prostanoids 1-4 and 6 were isolatedfrom the Okinawan softcoralClavularia viridis. The gross structure of 1 was elucidated mainly on the basis of NMR spectral data. The relative and absolute configurations were determined by analysis of NOESY and CD data, chemical conversion, and the modified Mosher's method. The structures of 2-4 and 6 were deduced by comparison of their spectral