The essential oil of Cyclospermum leptophyllum (Pers.) Sprague ex Britton and P. Wilson syn. Apium leptophyllum (Pers.) F. Muell. Ex Benth., family Apiaceae (Umbellifereae), was analysed by GC and GC-MS. The essential oil showed the presence of thymohydroquinone dimethyl ether (50.7%), thymol methyl