abstract the chemical composition and antimicrobial activities of essential oils isolated from myrrhis odorata, hypericum perforatum and helichrysum arenarium were investigated against seven bacterial and six fungal species. activity against the bacteria and c. albicans were investigated by a bioautographic test on tlc plates, while all the other fungi were tested by a microdilution test. the oil of h. arenarium showed the best antibacterial activity, while m. odorata oil showed the lowest effect, to compare with commercial products. in contrast, the best antifungal activity was observed for m. odorata oil, while h. arenarium showed the lowest antifungal potential. minimal inhibitory and fungicidal concentrations for fungi were 0.5-120 g/ml. the oil of m. odorata showed better activity then commercial product and it can be seen that this oil is very effective against all fungi tested.