The crystal structures of anhydroscymnol (I) and scymnol (II), which were prepared from sodium scymnol sulfate (III) isolated from the bile of Rhizoprionodon acutus, have been determined by means of X-ray diffraction analyses. The crystals of I are orthorhombic, space group P2(1)2(1)2(1) with Z = 4; unit-cell dimensions: a = 13.562(2), b = 21.636(2), c = 8.735(2) A; II orthorhombic, space group P2(1)2(1)2, with Z = 4; unit-cell dimensions a = 18.553(2), b = 19.887(2), c = 7.986(2) A. Both structures, (24R,25S)-(+)-24,26-epoxy-5 beta-cholestane-3 alpha,7 alpha,12 alpha,27-tetrol (I) and (24R)-(+)-5 beta-cholestane-3 alpha,7 alpha,12 alpha,24,26,27-hexol (II), were solved from diffractometric data by direct methods and refined by least-squares calculations to R = 0.073 (I) and R = 0.062 (II) (2044 (I) and 2250 (II) observed independent significant reflections (I greater than 3 sigma(I)), respectively. All the hydroxyl groups of both compounds are involved in a hydrogen-bonding network. The structure of III was determined to be (24R,25S)-(+)-3 alpha,7 alpha,12 alpha,24,26-pentahydroxy-5 beta-cholestan-27-yl sodium sulfate, based on the chemical data that alkaline degradation of III with aqueous potassium hydroxide gives only I.