Detailed GC and GC-MS analyses of oil of Melaleuca have identified several constituents not previously reported from Melaleuca alternifolia and clarified some earlier assignments. The range, mean, and coefficient of variation for the principle constituents in 800 typical samples are presented along with the compositions of several substandard oils. Isolation and storage procedures affecting the chemical composition of the oil are reported. Ethanolic extraction of mature leaves gave solutions suitable for direct injection into a gas chromatograph for the qualitative determination of tea tree oil. Comparison with conventional steam distillation showed that this technique was suitable for preliminary analysis of tea tree oil yield and quality.The essential oil of Melaleuca alternifolia Cheel (family Myrtaceae) was first reported early this century (Penfold, 1925) from the leaves of a paperbark tea tree growing in the central coastal region of eastern Australia. This taxon, previously known as Melaleuca linariifolia var. alternifolia, had been raised to species rank the previous year (Cheel, 1924), and the entire genus is at present undergoing taxonomic revision (Barlow, 1987, personal communication).Possible economic uses of the oil were immediately investigated as affinities with nutmeg oil were noted (Penfold, 1925; Penfold and Morrison, 1946) and high bactericidal activity was recorded (Penfold and Grant, 1925). Early reports list many medical conditions responding to treatment with oil of M. alternifolia (Penfold and Morrison, 1946;Guenther, 1950;Lassak and McCarthy, 1983).The oil was also used in machine "cutting" oils, as a perfumery toner and blender, and as a flavoring and antiseptic agent in denture and mouth washes (Guenther, 1950;Pickering, 1956). Consequently, the oil has maintained a place in the essential oil trade and has subsequently been investigated for use as a nutmeg flavor substitute (Pickering, 1956), in the treatment of furunculosis (Feinblatt, 1960), in combatting wood-destroying fungi (Maruzzella et al., 1960), in treatment of vaginitis (Pena, 1962), as an antiseptic in a "Water-Jel" fire blanket (Water-Jel, 1973), in veterinary products (Lassak and McCarthy, 1983), and as an additive to podophyllotoxin in oral contraceptives (Davis, 1984). An issue of Phytotherapy was dedicated principally to the medicinal uses of M. alternifolia oil (Belaiche, 1985; Carnero, 1985). Numerous studies have established the bactericidal and fungicidal efficacy of the oil against Bacillus typhosus, Staphylococcus aureus,
