The aim of this study was to examine the cytotoxicity and the antibacterial effects of a variety of essential oils on major respiratory tract pathogens. The cytotoxicity of 13 essential oils was evaluated on Vero cells. The antibacterial activity was evaluated by the Kirby Bauer paper method, minimum inhibitory and bactericidal concentration against Streptococcus pyogenes, agalactiae, pneumoniae and Klebsiella pneumoniae, Haemophilus influenzae, Staphylococcus aureus and Stenotrophomonas maltophilia isolated from clinical specimens. The antibiotic sensitivity of these isolates was examined. Some oils showed inhibition of bacterial growth against most of the organisms examined. Cinnamon and thyme showed the strongest action followed by clove. The results reported in this paper indicate that thyme can be considered as a potential antimicrobial agent for the treatment of some respiratory tract infections in man.