Abstract A hydrodistilled essential oil of the aerial parts of Ferula macrocolea (Boiss.) Boiss., an endemic species of Iran, was analyzed by GC/MS. Of the 55 components which were detected, 42 amounting to 86.3% were identified. The dominant components were Î²-pinene (15.9%), Î±-pinene (10.4%) and Î²-caryophyllene (8.6%).