Xanthium strumarium L. (Family: Compositae) a medicinal plant commonly found as a weed, is widely distributed in North America, Brazil, China, Malaysia and hotter parts of India. The herb is traditionally used mostly in treating several ailments. Extracts of the whole plant, especially leaves, roots, fruits and seeds have been applied in traditional medicine for the treatment of leucoderma, poisonous bites of insects, epilepsy, salivation, long-standing cases of malaria, rheumatism, tuberculosis, allergic rhinitis, sinitis, urticaria, rheumatoid arthritis, constipation, diarrhoea, leprosy, lumbago, pruritis, bacterial and fungal infections. This comprehensive account provides a botanical description of the plant, its phytochemical constituents and pharmacological activities are reviewed, focussing on antibacterial, antitumour, antitussive, antifungal, antiinflammatory, antinociceptive, hypoglycaemic, antimitotic, antioxidant, antitrypanosomal, CNS depressant activity, diuretic effects, contact dermatitis, insecticidal and herbicidal activities. Most of the pharmacological effects can be explained by the constituents like sesquiterpene lactones, glycoside, phenols, polysterols present in all plant parts. However, future efforts should concentrate more on in vitro and in vivo studies and also on clinical trials in order to confirm traditional wisdom in the light of a rational phytotherapy. Because of its multi-activity, in particular, anti-tumour, anti-cancer activity, so much attention is focussed on the herb. Finally, research needs quantitation of individual constituents and assessment of their pharmacological activities in humans.