The study was carried out on content and constituents of essential oil distilled from berries collected from Crimean Juniper (Juniperus excelsa) trees (called genotype in the paper) in a natural population. The immature and mature berries were collected from the trees in different aspects at the beginning, middle and end of growth period of 2010. The essential oil was obtained from berries by hydrodistillation. Its content and major constituents were compared for genotype, aspect and collection period. Environmental and genotypic effects on the content and constituent were also investigated. Results showed that while average of essential oil content was 2 %, it was 1.2 %, 2.3 % and 2.5 % for beginning, middle and end of growth periods, respectively. Eighty-eight constituents representing 99.2 % of the total essential oil were identified in different growth periods. The numbers of constituent were 30 at the beginning, 88 at the middle and 65 at the end of growth periods, while a-cedrol and a-pinene were major constituents. Averages of a-cedrol and a-pinene contents were 42.8 % and 17.4 %, respectively. The differences of the essential oil and major constituent contents were larger for growth periods than that of aspect and genotypes. Variation within clones was higher than that of among clones for the content of essential oil and major constituents. The result emphasized that non-genetic factors (i.e., collection period, aspect) were more important for the essential oil production and constituents of genotypes than their genetic constitution.