The compositions of the essential oils obtained from fresh capitula of Centaurea kotschyi var. kotschyi and Centaurea kotschyi var. decumbens, two endemic plants from Turkey, have been studied. Sesquiterpenes were the main components of both essential oils, with germacrene D (44.2%), β-caryophyllene (12.1%) and bicyclogermacrene (5.5%) in C. kotschyi var. kotschyi and germacrene D (29.4%), β-caryophyllene (11.2%), β-cedrene (7.1%) in C. kotschyi var. decumbens as the principal components. The qualitative and quantitative differences between the two essential oils are in agreement with the morphological observation that led to the differentiation of the two varieties. Copyright © 2003 John Wiley & Sons, Ltd.