Investigation of about 50 Senecio species has afforded many new substances, in addition to known compounds. Present in these plants are 23 furanoeremophilanes, nine triterpenes, 19 sesquiterpenes, a diynene, two euparine derivatives, two pyrrole derivatives and two norsesquiterpenes, one being the first naturally occurring oxepinderivative. The structures have been elucidated mainly by spectroscopic methods and by chemical reactions. The chemotaxonomic aspects are discussed. The overall picture is relatively clear, although there are still many unsolved problems regarding taxonomic subdivisions within this large genus.