Abstract The composition of the essential oil of Achillea ageratum L. from Corsica Island was investigated using a combination of gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS) after fractionation over column chromatography. Sixty-eight compounds were identified, the main components being 1,8-cineole (41%), yomogi alcohol (22.3%), santolina alcohol (10%) and artemisyl acetate (7.6%). The chemical composition of Corsican A. ageratum oil differed from those reported in the literature. The use of two capillary columns with different polarity under optimal GC conditions allowed the identifcation and the quantification of santolina alcohol that was coeluted on both capillary columns used. Key Word Index: Achillea ageratum Asteraceaeessential oilcomposition1,8-cineoleyomogi alcoholsantolina alcohol