The structure and stereochemistry of a new terpenoid ester, nardostachysin (1), isolated from the rhizomes of Nardostachys jatamansi, were established as the 7',8'-dihydroxy-4'-methylene hexahydrocyclopenta[c]pyran-1'-one-8'-methyl ester of 7, 9-guaiadien-14-oic acid, by spectral and chemical studies.