The chemical composition of essential oil obtained from the aerial parts of the Balkan endemic species Thymus longedentatus was studied by GC-MS. Twenty eight compounds, consisting 98.2% of the total components were detected in amounts exceeding 0.1%. The oil was characterized by relatively high concencentration of oxygentated monoterpenes (78.7%), among which citral isomers neral (27.5%) and geranial (30.3%) were the principal ones. In addition, 1,8-cineole (7.8%), trans-β-ocimene (7.5%), and β-myrcene (3.7%) were detected in significant ammounts. Germacrene D (4.4%) was found to be the main sesquiterpene in the essential oil.Se estudió mediante GC-MS la composición química del aceite esencial obtenido de las partes aéreas de Thymus longedentatus, especie endémica de los Balcanes. Se detectaron veintiocho compuestos, que representaban un 98,2% del total de compuestos y que se encontraban en cantidades superiores al 0,1%. El aceite se caracterizó por una concentración relativamente alta de monoterpenos oxigenados (78.7%), entre los cuales los isómeros de citral, neral (27.5%) y geranial (30.3%) eran los principales. Además, se detectó 1,8-cineol (7,8%), trans-β-ocimeno (7,5%) y β-mirceno (3,7%) en cantidades significativas. Se encontró que Germacreno D (4.4%) es el principal sesquiterpeno en el aceite esencial.