Résumé : Bicyclovetivene (V) and veticadinene (VI) have been prepared and isolated from the products of dehydration of a mixture of bicyclovetivenol (I) and veticadinol (II), tertiary sesquiterpenic alcohols of vetiver oil. Dihydrobicyclovetivene (VII) and dihydroveticadinene (VIII) were also obtained by dehydration of the corresponding dihydro‐alcohols. The structure of the diolefins (V and VI) and the olefins VII and VIII have been determined. The structures of the alcohols I and II could thus be deduced without being isolated. Bicyclovetivenol is seen to be the 2‐methylene‐6‐methyl‐9‐(β‐hydroxyisopropyl)‐bicyclo‐(0,3,5)‐decane (I) and veticadinol (II) is the 2‐methylene‐8‐methyI‐(β‐hydroxyisopropyl)‐bicyclo‐5‐(0,4,4)‐decane (II). Copyright © 1961 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim