Essential oils of the medicinal plants Satureja parvifolia, Satureja boliviana, Hyptis mutabilis, Leonorus sibiricus, Lippia turnerifolia, Xeroaloysia ovatifolia and Acantholippia salsoloides of north Argentina were analyzed by GC and GC/MS. Seventy-five compounds, representing more than 90% of the oils, were identified. The oils of both populations of S. parvifolia studied were characterized by a high content of piperitone (41.9% and 46%) and piperitenone oxide (50.1% and 49.3%). The most abundant constituents identified in S. boliviana oil were isomenthone (33%) and pulegone (25.3%). Hyptis mutabilis oil was characterized by β-phellandrene (27.1%) and β-caryophyllene (59.4%). The main constituents of L. sibiricus oil were the sesquiterpene hydrocarbons β-caryophyllene (35.2%), α-humulene (22.1%) and α-cubebene (18.4%). The oils of L. turnerifolia and X. ovatifolia also had a high content of sesquiterpenes. These were α-humulene (40.1%) and β-bisabolene (22.9%) in the oil of L. turnerifolia and β-caryophyllene (14.4%), (E)-nerolidol (10.5%), spathulenol (21.6%) and epi-α-cadinol (21.9%) in the oil of X. ovatifolia. Acantholippia salsoloides oil from Jujuy accumulated high contents of p-cymene (52.8%) and thymol (46.8%), while the oil from the population of Catamarca accumulated α-thujone (98.8%) as the major compound.