The essential oils from the aerial parts of Senecio nutans Sch.-Bip., collected in two different localities at 3500 and 4800 m above sea level in the Department of Arequipa, Perù, were obtained by hydrodistillation in 0.16% and 0.18% yields, respectively, related to the fresh weight. The oils were characterized by GC and GC-MS analyses. In the oil from plants at the lower altitude, 21 of 25 components were identified; the oil from the higher altitude site showed the presence of 46 components, 41 of which were identified. Monoterpene hydrocarbons predominated in both oils, with sabinene and α-terpinene as the main constituents. Copyright © 2003 John Wiley & Sons, Ltd.