Abstract The chemical composition of the essential oil obtained from the rhizomes of Acorus calamus (sweet flag) collected in the Grondines region, Province of Quebec, was determined by GC/FID and GC/MS analyses. Several components were isolated by liquid chromatography and were identified by various NMR experiments such as: 1H-NMR, 13C-NMR, HSQC, HMBC, and NOESY. The major compounds were identified as preisocalamenediol, acorenone, shyobunone, and cryptoacorone. The complete stereochemical structure of cryptoacorone was elucidated