Abstract The oil obtained by hydrodistillation of the aerial parts of F. microcolea (Boiss.) Boiss., which is endemic to Iran, and F. hirtella Boiss. were analyzed by GC and GC/MS. Thirty compounds representing 88.9% of the oil of F. mictocolea were identified, among them α-pinene (19.2%), nonane (13.2%) and β-pinene (13.0%) were the major ones. The oil of F. hirtella was also characterized by higher amounts of α-pinene (15.4%) and thymol (14.9%) among the 35 components comprising 84.8% of the total oil detected. Key Word Index: Ferula microcolea Ferula hirtella Umbelliferaeessential oil compositionα-pinenethymolnonaneβ-pinene