Sesquiterpene lactones are bioactive natural compounds with anticancer, antiprotozoal, immunomodulatory, antibacterial and antiviral activity which have potential for drug development. The aim of this review article is to provide a brief insight into the field of sesquiterpene lactones: the main mechanisms of their biological actions, as well as particular compounds, are described, some of which have already become a basis of a drug development and are being tested in clinical trials.