Essential oils extracted from dried leaves of Cupressus dupreziana A. Camus, an endemic species in the Tassili n'Ajjer (Sahara Central Algeria), were analysed by gas chomatography coupled to mass spectrometry (GC-MS). Terpinoid analyses were performed on 13 trees in the natural population of Hahadjerine in order to determine the intra-population variability. 39 trepenoids were identified; the averages of the principal components were transtotarol (24.4%), Manoyl oxide (21.2%), α-pinene (15%) and Δ3-carene (11.3%). The terpenoid markers used made it possible to determine the individual patterns of chemotypic variability. This variability confirms that genetic factors are not solely responsible for the decrease in the numbers of this species.