abstract the essential oils obtained by hydrodistillation from the stems, leaves, fruits and roots of smyrnium cordifolium boiss. growing wild in the northwest of iran were investigated by gc and gc/ms. the major constituents of the stem and fruit oils appeared to be curzerene (22.7% and 45.7%) and curzerenone (19.2% and 23.9%). the leaf and root oils were also characterized by high concentration of these compounds but in reversed order: curzerenone (21.8% and 56.6%) and curzerene (16.9% and 18.7%). hexadecanoicacid (13.6% and 18.7%) was also prodominant in the stem and leaf oils. in this study antibacterial activities of stem, leaf, root and fruit oils of s. cordifolium against seven gram-positive and -negative bacteria were determined by measuring the growth inhibitory zone. the oils showed significant anti-microbial activity against gram-positive bacteria. the oil of root and fruit inhibited the growth of salmonella typhi; the stem oil inhibited the growth of escherichia coli and pseudomonas aeroginosa. shigella flexneri was insensitive to the oil.