The water-distilled essential oils of Thymbra sintenisii Born, et Aznav. subsp. isaurica P.H. Davis and Origanum leptocladum Boiss., both Turkish endemic species, were analyzed by GC and GC/MS. Thirty-two compounds were characterized in the oil of T. sintenisii ssp. isaurica representing 96.64% of the oil, while 29 compounds were characterized in O. leptocladum oil representing 92.80%. The major components of T. sintenisii oil were carvacrol (39.01%), p-cymene (26.38%) and γ-terpinene (12.68%). The oil of O. leptocladum also contained p-cymene (47.09%) and carvacrol (14.61%) as major components along with borneol (10.80%). © 1996, Taylor & Francis Group, LLC. All rights reserved.