The composition of hydro-distilled essential oils from fresh leaves of wild growing Juniperus polycarpos var. turcomanica, collected from northeaste of Iran, were investigated by GC and GCâMS analysis during growing season 2012â2013. The oil yields depend on the month of collecting and ranged between 1.5 and 2.1% (v/w). Analysis of the essential oil identified 49 components that representing 89.7â94.6% of the total oil. Results indicated that the predominant presence of monoterpene constituents, representing 56.9â85.6% of the essential oil. The main constituent was Î±-pinene (41.8â75.4%), followed by germacrene B (1â5.8%), camphor (0.7â4.5%) and Î±-cadinol (0.4â4.8%). Regarding essential oil composition, quantitative and qualitative variations were recorded for 12 different collection periods. The best time for harvesting juniper leaves seems to be from mid-autumn to mid-winter.