Abstract The composition of the essential oils from three Umbelliferae species of Iran -Alococarpum erianthum (DC) H.Riedl et Kuber., Ferula ovina (Boiss.) Boiss. and Pimpinella affinis Ledeb.-were obtained by hydrodistillation and analyzed by GC and GC/MS. During the flowering period, two oils (A. erianthum and F.ovina) consisted mainly of monoterpenes, while in P. affinis oil sesquiterpenes predominated over monoterpenes. The oils of A. erianthum and F.ovina were rich in Î±-pinene (46.5% and 50.0%) and limonene (10.1% and 11.5%), respectively. In the oil of P. affinis, trans-Î±-bergamotene (56.2 %) and (E)-Î³-bisabolene (11.3 %) were found to be the major constituents