The components of the essential oil obtained from the dried aerial parts of Sideritis trojana Bornm. by hydrodistillation was analyzed both by GC-FID and GC-MS, simultaneously. Overall 57 compounds were identified representing 83.8% of the oil. The major components of the oil were identified as valeranone (11.3%), alpha-bisabolol (10.9%) and beta-caryophyllene (8.8%), respectively. The composition of the oil showed quantitative chemical variation from previously studied material in terms of its major components. Moreover, the essential oil was evaluated for its in vitro antibacterial and anticandidal activities using a broth microdilution method. A selected panel of standard strains of Gram (+) and Gram (-) human pathogens as well as Candida albicans were used in the assay. As a preliminary result, it was observed that the oil displayed relatively moderate antibacterial activity against Helicobacter pylori with MIC value of 250 mu g/mL when compared to standard antimicrobials. As a conclusion, it is worthwhile to evaluate the plant material against a broader spectrum of activities.