Turkish oregano (Origanum onites L.) is a major aromatic plant that belongs to Labiatae family. In this work fourteen Turkish oregano clones have been characterized chemically and genetically. Essential oil obtained by hydro-distillation was characterized by gas chromatography. Genetic variation was determined by use of random amplified polymorphic DNA (RAPD) markers. Variation of essential oils in the selected clones was subjected to cluster analysis, and two chemotypes, carvacrol and thymol, were identified. Carvacrol was found to be the main component in all clones except clone-661, the main component of which was thymol. The oregano clones were divided into three main groups by clustering on the basis of RAPD markers. Genetic similarity values among the oregano clones ranged between 0.49 and 0.73 which was indicative of a low level of genetic variation. Clones originating from locations close to each other had similar RAPD markers. Correlation analysis of the genetic distance matrix and the Euclidian distance matrix revealed no significant correlation between them. The results also indicated that there is no relationship between genetic structure of the selected clones and essential oil composition.