The genus Achillea L. (yarrow) comprises over 100 perennial herb species indigenous to the Northern Hemisphere. In Lithuania Achillea millefolium L. s.l., the best-known and most widespread species of yarrow, is listed amongst the most commonly used plant species in both folk and conventional medicine. The diversity and complexity of the phytochemical composition of yarrow species may explain their polyvalent pharmacological activity. The raw material of A. millefolium L. s.l. contains terpenes, alkaloids and bases, tannins, coumarins, saponins, sterols, vitamins, amino and fatty acids. Phenolic compounds, such as ﬂavonoids and phenolcarbonic acids, constitute one of the most important groups of pharmacologically active principles in yarrow. It is suggested that anti-inﬂammatory, antimicrobial, choleretic and cytotoxic activities of Achillea plants are mainly attributed to the ﬂavonoid and phenol-carbonic acid complex. However, further scientiﬁc investigations are still required to clarify its phytochemicals as well as the spectrum of their potential utilisation.