Abstract: Genetic variation in monoterpenes foliage was determined in natural populations of Cupressus dupreziana A. Camus. Samples were obtained from 12 populations in 12 regions from Tassili n’Ajjer (Central Sahara of Algeria). A total 20 monoterpenes were detected, with a particular abundance of α-pinene and Δ3-carene. Terpenoids markers allowed the detection of individual chemotypic variability. The high variability found in the monoterpene composition suggested that genetic basis was not the main factor contributing to the extinction of this species. It seems most probable that the reduced population size of this species is related to the effect of Tassili n’Ajjer desertification.