The chemical composition of the essential oils of Achillea holosericea, Achillea taygetea, Achillea fraasii was determined by GC/MS analysis. Among the ninety-five assayed constituents, camphor, borneol and 1,8-cineol were found to be the major components. The in-vitro antimicrobial activity of these essential oils was evaluated against six bacteria indicating that the first is totally inactive, while the other two possess moderate to strong activities mainly against the Gram negative strains. The essential oil of A. fraasii was also active against the tested pathogenic fungi.