The leaf oil of the red juniper was found to contain mainly sabinene, as well as limonene, α-pinene, γ-terpinene, terpinolene, 3-carene, myrcene, 4-terpinenol, citronellol, elemol, γ-, α-, and β-eudesmol, the aromatic ethers estragole, safrole, methyl eugenol, and elemicin. Another aromatic ether, methyl vinyl anisole, was isolated which has not been found previously in essential oils. The acetates 1 and 2 obtained previously in two related juniper leaf oils were present and the first has been identified as elemol acetate. Small amounts of α-thujene, p-cymene, linalool, and δ-cadinene were also identified.Quantitative aspects were studied with a view of future chemosystematic investigations. The error in duplicate runs was 0.1% for well-resolved peaks, but the absolute error, as determined by use of internal standards, was larger. Leaf oils of different trees from Texas and Ontario were found to give wide quantitative variations of the individual components.