abstract the essential oil obtained by simultaneous steam distillation and extraction (sde) from air-dried aerial parts of plant species achillea millefolium l. yarrow was analyzed by capillary gc and gc/ms. sixty-six components were identified. the major constituents in the oil extracts were -pinene (14.9-29.2%), sabinene (2.9-17.6%), 1,8-cineole (6.9-18.3%), -caryophyllene (3.3-6.2%), (e)-nerolidol (0.5-6.4%), guaiol (0.3-11.8%) and chamazulene (0.1-13.3%). the monoterpene fraction represented 41-61% of the total oil. the increasing of distillation time from 0.5-3 h increased the yield of oil ca. two-fold, at the same time the chamazulene content increased ca. three-fold. the yield of oil after two hours distillation was 2-4 mg/g. the oil yield from the flowers was two times higher than from the leaves, while it was very low from the stems. the oil from the leaves and especially from the stems contained more oxygenated aliphatic compounds, diterpenoid compounds and other highboiling compounds, and less chamazulene and sesquiterpenes than oil from the yarrow flowers.