Abstract Porophyllum ruderale Cass. (Asteraceae) (1) is a medicinal plant from Brazil. Oils produced by steam distillation from leaves and roots were analyzed by GC/MS and retention indices. The leaf oil showed limonene (75.2%) and (E,E)-dodecadienal (15.5%) as main constituents. The major components found in the root oil were davanone-2-ol (22.7%) and isocomene (16.7%).