New acetylenic sterols, gelliusterol A (1, 26,27-bisnorcholest-5-en-23-yn-3
beta ,7 alpha -diol), its corresponding 7-ketone, gelliusterol B (2, 26,27
-bisnorcholest-5-en-23-yn-3 beta -ol-7-one), and gelliusterols C (4, choles
t-5-en-23-yn-3 beta ,7-one) and D (5, cholest-5-en-23-yn-3 beta ,25-diol-7-
one), were isolated from an unidentified species of sponge, Gellius sp. The
structures of the steroids were established from spectroscopic data.