The structure of this 14 alpha-acetoxy-13 alpha-hydroxymulin-11-en-20-oic acid monohydrate consists of a mulinane skeleton and the corresponding isopropyl, methyl, carboxyl and methyl groups at C3, C8, C5, C13, respectively, which are beta-oriented, whereas the hydroxyl and acetoxy groups at C13 and C-14 are -alpha oriented. The cyclopentane (A), cyclohexane (B) and cycloheptene (C) rings are trans (A/B) and (B/C) cis fused, and in an envelope, chair, and twist conformation respectively. In the crystal the organic molecules are linked by the water molecules by two intermolecular O-H center dot center dot center dot O hydrogen bond forming 1D-dimensional chains with graph-set notation (9).