The isolation of a precursor (I) of geijerene (II) from Geijera parviflora Lind. supports the view that elemane-type sesquiterpenes may arise by Cope rearrangements of terpenoid cyclodecadienes. We report that the sesquiterpene alcohol, elemol, is indeed such an artefact in one essential oil, and suggest that this may be generally true of elemol and the elemenes. The essential oil of Hedycarya angustifolia A. Cunn., described as a rich source of elemol (III), when extracted at room temperature yields principally a new sesquiterpene alcohol, hedycaryol, and only a trace of elemol. Hedycaryol (C₁₅H₂₆O) is converted to elemol upon heating. From the evidence presented and by analogy, hedycaryol is suggested to possess structure (IV) and be the precursor of the elemol found in H. angustifolia oil. Java citronella oil, another source of elemol, yields a mixture of elemol and hedycaryol as well as a hydrocarbon which undergoes thermal isomerization to β-elemene. Whether elemol is ever a natural product rather than an artefact remains to be determined.