Abstract The essential oils of Scutellaria sieberi and S. rupestris ssp. adenotricha from Greece were analyzed by means of GC/MS. Forty-nine constituents were identified representing 87.1% and 81.4% of the oils, respectively. Linalool (22.7%), Î²-caryophyllene (14.2%), (2R, 5E)-caryophyll-5-en-12-al (6.3%) and (2S, 5E)-caryophyll-5-en-12-al (14.1%) were the major components of S. sieberi, whereas in S. rupestris ssp. adenotricha linalool (38.8%), geraniol (8.1%) and Î±-terpineol (7.1%) were the major components. Furthermore, the oils were tested against H. pylori, as well as against six aerobically growing bacteria. Key Word Index: Scutellaria sieberi S. rupestris ssp adenotricha Lamiaceaeessential oil compositionlinaloolÎ²-caryophyllene(2S, 5E)-caryophyll-5-en-12-alantimicrobial activity