Eryiğit, T., Okut, N., Ekici, K. and Yildirim, B. 2014. Chemical composition and antibacterial activities of Juniperus horizontalis essential oil. Can. J. Plant Sci. 94: 323–327. In recent years, the screening of antibacterial activity has been the subject of much research, and the antibacterial activity of essential oils could be a promising subject for future investigation. In this study, the antibacterial activities of Juniperus horizontalis essential oils and their components were investigated. Essential oils were isolated using the hydro-distillation method and their components were analyzed by gas chromatography–mass spectrometry (GC-MS). The main compounds found in the oil of leaves were linalool (33.76%), P-cymene (23.20%), gamma-terpinene (8.67%), trans-sabinene hydrate (8.59%), thyme camphor (8.49%), carvol (5.08%) and borneol (4.22%). Juniperus horizontalis essential oils were evaluated for antibacterial activity against six bacterial strains using the disc diffusion method. The results indicate that the essential oil of J. horizontalis shows variable and significant antibacterial activities against the six tested bacteria species. The diameters of the inhibition zones formed for bacteria were measured. The lowest inhibition zone was 12 mm (sensitive) against Pseudomonas aeruginosa ATCC 10145 and the highest zone was 32 mm (extremely sensitive) against Enterococcus faecalis ATCC 29212.