Essential oils are aromatic and volatile liquids extracted from plants. The chemicals in essential oils are secondary metabolites, which play an important role in plant defense as they often possess antimicrobial properties. In this study, essential oils of four plants were investigated for their antimicrobial activity against eight bacterial pathogens and seven fungal strains. The used plants were Salvia officinalis, Thymus vulgaris, Eugenia caryophyllata and Artemisia absinthium. All of plants essential oils showed antibacterial and antifungal activities. Zones of inhibition against pathogenic bacteria ranged from 10 to 28 mm and MIC from 25 to 150 µg/ml, while zones of inhibition against fungal strains ranged from 10 to 26 mm and MIC from 25 to 150 µg/ml. Cytotoxicity against Artimia salina and antitumor activity against Ehrlich ascites carcinoma and Lymphoma cell line were investigated. A. absinthium showed the best antitumor activity on Lymphoma cell line with moderate cytotoxic effect on Artimia salina. Analysis of A. absinthium essential oil by GC-MS discovered two major compounds; camphor and fenchone which may be involved in the biological activity of the plant extract