Abstract The volatile constituents of the aerial parts of Centaurium erythraea Rafn obtained by hydrodistillation were analyzed by GC and GC/MS. Two hundred and thirty two constituents identified accounted for 93.4% of the total oil. The major components of the oil were: neophytadiene isomer III (10.1%), carvacrol (7.9%), p-camphorene (5.6%), hexadecanoic acid (4.9%) and thymol (4.2%). The terpenoid fraction represented more then one half of the oil (14.4% monoterpenoids, 18.7% sesquiterpenoids and 22.4% diterpenoids), while the fatty acids and fatty acid derived compounds made up a third, and the carotenoid derived compounds only ca. 5% of the oil. Erythrocentaurin, 5-formyl-2,3- dihydroisocoumarin, although a minor contributor (0.1%) of the oil, was identified for the first time in an oil sample. Key Word Index: Centaurium erythraea Gentianaceaeessential oil compositionneophytadienecarvacrolp-camphoreneerythrocentaurin