The essential oil obtained from the aerial parts of Thymus Kotschyanus Boiss. & Hohen var. kotschyanus, growing wild in Iran, was analyzed by using GC and GC-MS. There were 10 compounds in the volatiles from T. Kotschyanus var. kotschyanus, comprising 97.38% of the total oil in 0.93 % (w/w) yield. The main constituents of the species were Thymol (89.08%) and γ-Terpinene (4.62%). Three common chemical compositions namely, a-Pinene, Borneol and Thymol, have been found among six populations. There is not Carvacrol in T. kotschyanus var. kotschyanus which is the major difference between this study and the previous ones. On the other hand, Gadouk Col population represents the highest amount of Thymol (89.08%) in its essence. The quantitative and qualitative differences in the volatile constituents can be considered as chemotaxonomic significance and it may be attributed to their different ecological and geographical origin factors.
