The lipid extract of the Sclerophytum so. of soft coral, collected off the coast of the Andaman and Nicober Islands, afforded a new sterol 1a. The structure of 1a was shown to be (24S)-3β-hydroxyergost-5-en-21-oic acid, the first member of a class of marine sterols having a C-21 carboxylic acid, by spectral analyses and conversion to(24S)-ergostane.