The aerial parts of Xanthium pungens, collected near El-Minia, Egypt, afforded, in addition to several known sesquiterpene lactones and some other compounds, a lactone with a new carbon skeleton, two dimeric sesquiterpene lactones, an endoperoxide, an 11,13-dihydroxanthanolide and a further sesquiterpene acid. The structures were elucidated by highfield NMR techniques. The structure of the pentacyclic lactone was confirmed by partial synthesis from 8-epixanthatin.