The leaves of Heracleum persicum Desf. ex Fischer (Syn. H. glahrascens Boiss. & Hohen, H. pubescens Rech.) (Fam. Apiaceae) were collected in July-Auguest 1993 from Kandavan area in north of Tehran. The oil was extracted by hydrodistillation (0.13%) from leaves and was analyzed by GC, GC/MS and lH-NMR. The major component was trans-anethole (82.8%). Other components were p-pinene, p-cymene and terpinolene (monoterpenes), α-caryophylene, α-bergamotene, α-farnesene, zingiberene, spathulenol (sesquiterpenes), cis-anethole, stragole, 2,5-dimethyl styrene (aromatic compounds), and β-springene (an aliphatic and hydrocarbonic diterpene). It is concluded that this oil is a source of trans-anethole.