Variations in the essential oil content and composition in commercial samples of yarrow (n = 12) obtained from retail pharmacies and in wild yarrow with white and pink flowers (n = 2) were determined by applying hydrodistillation and capillary GC techniques. The yields of oil in 14 samples were ranged from 0.11 % to 1.03 %. In 12 samples the yields were in accordance with the European Pharmacopoeia requirements (not less than 0.2 % of essential oil). 92 components, comprising more than 90 % of the total volume of oil, were identified. The quantitatively most important components of the oil were chamazulene (0.8 - 44.3 %), beta-pinene (tr - 23.3 %), sabinene (0 - 16.5 %), bornyl acetate (tr - 15.8 %), (E)-beta-caryophyllene (2.5 - 14.3 %), (E)-nerolidol (tr - 9.6 %), 1,8-cineole (tr - 9.6 %), and germacrene D (0.2 - 7.8 %). Chemotypes of chamazulene, chamazulene + bornylacetate, chamazulene + beta-pinene + (E)-beta-caryophyllene, sabinene + 1,8-cineole, and beta-pinene + alpha-terpinyl acetate were analysed. The amount of chamazulene was in a negative correlation with the amounts of (E)-nerolidol (r = -0.673, p < 0.01) and with sabinene (r = -0.546, p < 0.05). The quality of yarrow commercial samples was remarkably variable, especially in yields of essential oil and in the content of main constituents.