The genus Achillea consists of about 140 perennial herbs native to the Northern hemisphere. Traditional indications of their use include digestive problems, liver and gall-bladder conditions, menstrual irregularities, cramps, fever, wound healing. The Commission E approves its internal use for loss of appetite and dyspeptic ailments (gastric catarrh, spastic discomfort), externally it is used in form of sitz bath or as a compress against skin inflammation, slow healing wounds, bacterial or fungal infections. In the last decades, pharmacological studies became intensive, although human clinical investigations are still rare. Recent findings have confirmed several traditional uses. The largest number of data accumulated for antioxidant and antiinflammatory effects. There are positive results on the analgesic, anti-ulcer, choleretic, hepatoprotective and wound healing activities. First results on other interesting therapeutical areas – antihypertensive, antidiabetic, antitumor, antispermatogenic activities – need confirmation. Yarrow can be used also as an insect repellent. Contact dermatitis as adverse effect may be connected to sesquiterpenes. The diversity and complexity of the effective compounds of yarrow species explains the broad spectrum of their activity. According to the literature the pharmacological effects are mainly due to the essential oil, proazulenes and other sesquiterpene lactones, dicaffeoylquinic acids and flavonoids. Synergistic actions of these and other compounds are also supposed. Achillea species have different chemical and therapeutical values. Despite of numerous data, correct evaluation of the results is difficult because of missing generally accepted taxonomical nomenclature. The used chemical-analytical methods and bio-assays are utmost diverse, making the comparison complicated. Further research on the activity is needed using exactly defined plant material, standardized methods and chemical analysis.