The chemical constituents of essential oil by hydrodistillation from the aerial parts of Hyssopus officinalis L. and Origanum acutidens (hand.-mazz.) ietswaart from Turkey were identified by gas chromatograph-mass spectrometer (GC-MS) demonstrated the presence of at least 24 compounds. The major constituents of H. officinalis oil were pinocarvone (29.2 %), trans-pine camphone (27.2 %), β-pinene (17.6 %), cis-pinocamphone (4.7 %) and myrcene (2.92 %). The major constituents of the essential oil of O. acutidens were carvacrol (76.2 %), p-cymene (7.4 %) and borneol (3.2 %). © 2012, Copyright Har Krishan Bhalla & Sons.