The composition of the water-distilled essential oil of Achillea multifida (DC.) Boiss. (Compositae) was analysed by GC and GC/MS. Fifty-eight compounds were identified representing 93.9 % of the total oil. alpha-Thujone (60.9 %), beta-thujone (9.1 %), sabinene (4.1 %) and camphor (3.7 %) were characterised as the main constituents. The essential oil was tested for its antimicrobial activity using a micro-dilution assay resulting in the inhibition (MIC: 62.5-250 microg/ml) of human pathogenic bacteria and yeast.