Sesquiterpene lactones are a large group of secondary plant metabolites mostly known from the Asteraceae family. They exert a broad variety of different biological activities. This review attempts to critically summarise the knowledge on the anti-inflammatory and cytotoxic activity of SLs, with a special focus on parthenolide and helenalin. Recent advances on their molecular modes of action, allergic potential and also QSAR studies with SLs are presented. Therapeutic areas are highlighted in which SLs may play a role in the future. Thus, SLs may possess therapeutic relevance as single components for the local treatment of inflammation, such as rheumatoid complaints. In cancer therapy, SLs may be favourable in dual therapy or in the inhibition of leukaemia cell growth. In each case, native SLs serve as leads that have to be optimised in terms of their specificity, pharmacokinetics and absorption, distribution, metabolism and excretion (=ADME) properties. Finally, appropriate in vivo studies will decide whether SLs will become therapeutics or remain interesting research compounds.