Résumé : Cholest‐6‐en‐11β, 19‐epoxy‐3β, 5α, 8α, 9α‐tetrol(1), a new toxic polyoxygenated steroid, has been isolated from the sponge Dysidea tupha. Its structure has been determined on the basis of its spectral properties. Copyright © 1988 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim