Abstract This is first report on the composition of the leaf essential oils of J. communis L. varieties from the Western Hemisphere. The oil of Juniperus communis var. jackii had the most distinct oil and contained moderate amounts of α-pinene (16.1â18.9%), δ-3-carene (17.9â28.4%) and β-phellandrene (9.2â13.4%) along with several diterpenes including isoabienol. Juniperus communis var. charlottensis oil had a very high concentration of α-pinene (59.3%), with moderate amounts of β-pinene (5.9%), δ-3-carene (3.6%) and β-phellandrene (2.9%). The oil of J. communis var. depressa was dominated by α-pinene (53.9%), δ-carene (9.3%) and β-pinene (5.5%) and was a little unusual in also containing citronellol, citronellyl acetate, neryl acetate and geranyl acetate with no diterpenes. The oil of J. com-munis var. megistocarpa possessed large amounts of α-pinene (58.5%), limonene (20.4%) and β-pinene (5.0%) and, like J. communis var. depressa, its oil also contained citronellol, citronellyl acetate, neryl acetate and geranyl acetate. Putative J. communis var. saxatilis from Idaho, USA, had a high concentration of α-pinene (56.5%) with moderate amounts of δ-carene (11.5%), β-pinene (5.4%), myrcene (4.5%) and β-phellandrene (3.1%). The oils of these North American varieties were compared to J. communis var. communis (Sweden) and J. communis var. saxatilis (Switzerland). A survey of approximately 65 species of Juniperus revealed that isoabienol was present in eight species. X-ray, MS and 13C-NMR were used to determine the structure of isoabienol (I) and KI and a mass spectrum is presented to aid future Identification.