the essential oils obtained from the aerial parts and the roots of conyza canadensis (l.) cronquist (asteraceae) at the flowering stage, collected from turkey were simultaneously analysed by gc-fid and gc-ms. forty-six components comprising 82.8% of the essential oil from the aerial parts and seven components comprising 96.7% of the roots oil were identified. major constituents of the essential oil of the aerial parts were found to be limonene (28.1%), spathulenol (16.3%) and -pinene (9.7%), whereas cis-lachnophyllum ester (86.5%), (2z,8z)-matricaria ester (3.9%) and -pinene (2.3%) were identified to be main constituents in the volatiles of the root parts. in addition, antimicrobial activity of the essential oils was screened against gram-positive and gram-negative bacteria as well as one strain of fungus by broth microdilution method. both of the essential oils exhibited antifungal activity against candida albicans atcc 10231 with 0.078 g/ml mic values. the highest antibacterial activity was observed by aerial parts oil against escherichia coli rskk 234 (mic: 0.039 g/ml). this is the first report on the chemical composition and antimicrobial activity of the essential oils obtained from c. canadensis growing in turkey.