The rate and main components of essential oil from aerial parts of Thymus praecox ssp. scorpilii (Velen) Jalas var. laniger (Borbas) Jalas were investigated. For the purpose, samples of the species were collected from three altidutinal populations at Southern part of Turkey at flowering stage of the species. The essential oil obtained by hydrodistillation were analysed by GC-MS to determine its components. The rate of essential oil changed in the populations, with an average of 2.26%. Thymol and carvacrol were characterized as main components of the essential oil according to GC-MS analysis, while their rates were changed according to the populations. The averages of thymol and carvacrol were 48.10% and 22.20%, respectively. Thymol, thymol-carvacrol and carvacrol-thymol were determined as chemotypes. Altitude was significantly (p <= 0.05) effective on essential oil, carvacrol and thymol rates according to results of correlation analysis. Variations in essential oil rates and compositions may be due to on genetic, ecological or individual variability. (C) 2011 Friends Science Publishers