5 alpha-Dihydrorubrosterone (2 beta, 3 beta, 14 alpha, 17 beta-tetrahydroxy-5 alpha-androst-7-ene-6-one), a new 19-carbon 5 alpha-ecdysteroid, was isolated together with its 5 beta counterpart from the aerial parts of Silene otites L. (Wib.) (Caryophyllaceae) by a combination of solvent partition,