AbstractTwo novel pregnatrienolones isolated in very small amounts from the North‐East‐Atlantic demospongeAxinella agnata(Tetractinomorpha, Axinellida) are unique in having C(2)C(3) (or C(3)C(4)), C(7)C(8), and C(16)C(17) bonds and a 12β‐OH group which, being strongly H‐bonded to a 20‐keto group, resists acylation.1H‐ and13C‐NMR spectroscopy of the steroids and of products of their selective epoxidation or reduction allow us to propose the structures (+)‐12β‐hydroxy‐5α‐pregna‐2,7,16‐trien‐20‐one ( = agnatasterone A, (+)‐1), and (+)‐12β‐hydroxy‐5α‐pregna‐3,7,16‐trien‐20‐one ( = agnatasterone B. (+)‐5),