Abstract The essential oil of Eryngium foetidum leaves from S. Tomé e Príncipe was investigated for the first time. The oils were obtained by hydrodistillation of the leaves, from two different sites, and subsequently analyzed by GC, GC/MS and 13C-NMR. The oils were characterized by the presence of small amounts of monoterpene hydrocarbons and sesquiterpenoids, and by a large number of aromatic and linear aldehydes in high proportions, with 2,3,6-trimethylbenzaldehyde (5.5â23.7%), (E)-2-dodecenal (15.9â37.5%) and (E)-2-tetradecenal (18.7â25.3%) being the most dominant.