Conium maculatum L., a member of the Apiaceae (formerly Umbelliferae) family of rhizomal plants [1], is an annual, biennial, or, in favorable conditions, perennial plant, usually 120-180 cm high. C. maculatum (hemlock, poison hemlock) is a very common and worldwide plant species. It is one of the most toxic plants known [1]. Poison hemlock is native to Europe and western Asia and has been brought to America and Oceania as an ornamental plant [2]. A "cocktail" of an extract from C. maculatum, mixed with opium has been reported to be the lethal poison which the Greek philosopher Socrates was condemned to drink in the year 399 B.C. [3].Despite being a worldwide renowned plant species and being a member of the family of numerous aromatic plant species (some of them containing significant quantities of volatile constituents), the essential oils of this plant species were the subject of only two previous studies. Only recently was the chemical composition of the Iranian C. maculatum essential oil published [4]. Previously, a study concentrating on antifeedant compounds from C. maculatum reported only the major volatile constituents of this species [5].Having in mind the scarce data on the volatile constituents of C. maculatum (and the genus Conium in general) and the non-existence practically of any information on plant part specification of the essential oil, we decided to investigate the chemical composition of the hydrodistilled leaf and flower essential oils of Serbian C. maculatum.The yields of yellowish, transparent essential oils of noxious odor obtained from fresh leaf and inflorescence of C. maculatum were 0.04 and 0.06% (v/w), respectively. The essential oils were analyzed by GC and GC-MS and the resulting data on the qualitative and quantitative chemical composition are presented in Table 1. Twenty-three and fifty-seven constituents were identified in the leaf and flower oils of C. maculatum, accounting for 96.2 and 97.5% of the total oils, respectively.The major constituent in both flower and leaf oils was germacrene D (27.2 and 41.0%, respectively). The two runnersup in the leaf oil were the acyclic monoterpenes (Z)-β-ocimene (7.1%) and (E)-β-ocimene (22.3%), while in the inflorescence oil the second and third most abundant components were (Z)-β-ocimene (14.3%) and β-myrcene (9.3%). The relative amounts of (E)-b-ocimene (7.7%) and (E)-nerolidol (7.1%) in the flower oil deserve mention as well. The monoterpene and sesquiterpene fractions of the oils were comparable in their relative amounts (flower oil: 40.1% monoterpenes versus 46.3% sesquiterpenes, leaf oil: 33.6% monoterpenes versus 54.6% sesquiterpenes Table), and the number of identified monoterpenes and sesquiterpenes followed the same trend (13 and 19). However, within the fractions a highly uneven distribution between the hydrocarbons and oxygenated derivatives was observed, with a prevalence of non-oxygenated compounds ( Table 1).The leaf and flower oils were characterized by the presence of "green-leaf" volatiles, formed by unsaturated fatty acid ...