The chemical compositions of the essential oils of Pituranthos chloranthus harvested at the vegetative, flower budding, flowering and fruiting stages from three distinct geographical areas of Tunisia were investigated using GC-FID and GC-MS. One hundred and fifty compounds were identified in which alpha-pinene, beta-pinene, alpha-phellandrene, beta-myrcene, beta-phellandrene, p-cymene, 8-methyldecanal, exo-2-hydroxycineole acetate and carvacrol could reach more than 10% of the total amount. However, this composition varied with respect to both the geographical area and the season. A clear discrimination of samples could be achieved by submitting the results to PLS discriminant analysis. p-Cymenene was only detected at the floral budding stage (February), whereas high amounts of exo-2-hydroxycineole and exo-2-hydroxycineole acetate were specific for the flowering period (April). Carvacrol was showed to be characteristic mainly of the fruiting period (August), whereas the vegetative state (November) could be distinguished from the others by the presence of alpha- and beta-pinene. Limonene, camphene, geraniol and beta-damascenone were likely to be specific for the essential oils of this species collected from the different regions of Tunisia.