The oleoresin of Pistacia atlantica Desf. ssp. atlantica, growing wild in different and and semi-arid regions of Algeria, is a popular naturally-occurring chewing gum and has been used traditionally in the treatment of peptic ulcer. GC/MS analysis of the essential oil obtained from solvent distillation of the fresh oleoresin has led to the identification of many terpenoids: alpha-pinene (39.4%), beta-pinene (12.9%), carvacrol (11.8%), pinocarvone (5.5%), limonene (5.1%), germacrene-D (2.4%), trans-pinocarveol (2. 1 %), camphenol (2%), borneol (2%), alpha-terpene (1.8%), p-cymene (1.7%), terpinolene (1.4%), terpinene-4-ol (1.4%), isopinocarveol (1.1%) and verbenene (1.0%). Other minor constituents were also identified.