Bathurst burr (Xanthium spinosum L.) is an invasive species that is also known as a medicinal plant. Our goal is to make known the plant and its therapeutic effects in larger scale. The plant has been used in the Romanian folk medicine for urinary problems and various prostate diseases. The most important substances in Xanthii spinosi herba are: flavones and their derivates (quercetin, pendulin, iocein, centaurin and patuletin), polyphenols (caffeic- and chlorogenic acid and their derivates), sesquiterpene lactones (xanthinin, xanthatin-xanthanol-xanthumin derivates), diterpenes (atractyloside and derivates) and phytosterols (sitosterol, stigmasterol). The beneficial effect of the herb was proved in the 80's by Petcu and his collaborators. The plants infusion and tincture had positive effects on induced benign prostate hyperplasia in rats. The antibacterial and antifungal properties of the plant are attributed to the sesquiterpene lactone, xanthatin. Our preliminary experiments showed the presence of the xanthatin in the toluol, chloroform, methanol and ethanol extracts.