The structure of the rare sesquiterpene 9-epi-beta-caryophyllene, isolated from the foliage of the New Zealand rimu tree, Dacrydium cupressinum was verified by 2D NMR techniques and the relative stereochemistry determined by NOE studies. The absolute stereochemistry was determined by conversion of both beta-caryophyllene and 9-epi-beta-caryophyllene into the same known [7,2,0(1,6),0(1,9)] tricyclic compound. Molecular modelling results on the lowest energy conformations of beta-caryophyllene and 9-epi-beta-caryophyllene were in agreement with experimental results.