The similarities of some species of the genus Thymus L. (Labiatae) from Turkey, were studied using the morphological and chemical characters. Chemical analyses were carried out by gas chromatography/mass spectrometers. For each taxa, 20 quantitative characters and 130 volatile oil substituents were determined and the data subjected to numerical taxonomic analyses. The results exhibited that the dendrograms obtained from morphological and chemical data were similar. To the results, the closest taxa were T. sipyleus Boiss. and T. leucotrichus Hal. Likewise, T. praecox Opiz., T. longicaulis C. Presl. and T. thracicus Velen. were closely related species. However, T. pseudopulegioides Klokov and Des. Shost was distinct from the other taxa. © 2006 Asian Network for Scientific Information.