The chemical composition of the essential oils from fresh leaves of four species (Artemisia sodiroi, Siparuna eggersii, Tagetes filifolia and Clinopodium nubigenum), grown wild in the southern Ecuador (province of Loja), was examined through the GC-MS analysis. In the essential oil of A. sodiroi, the oxygenated monoterpenes were the main group of components, especially sabinyl acetate (65.8 %), while the essential oil of S. eggersii was mainly composed by the oxygenated sesquiterpenes among which the epicurzerenone (29.9 %) was the most representative. Conversely, the aromatic hydrocarbons predominated in the oils of T. filifolia and C. nubigenum, with (E)-anethole (72.6 %) and carvacryl acetate (38.1 %) as the main components, respectively.