Several plants and plant-derived pure compounds, designated as phytoestrogens, have been reported to cause estrogenic effects. They have been used for alleviation of menopausal symptoms, prevention of osteoporosis, heart disease and cancer. There is an increased interest in studying phytoestrogens such as isoflavones and lignans for their use as replacements for synthetic estrogens. In this study, the estrogenic activity of essential oils of eleven Pimpinella species and the compounds isolated from these species were evaluated using the yeast estrogen screen (YES) assay. The essential oils containing (E)-anethole as major compound showed estrogenic activity in the YES assay, except for the aerial parts without fruits of P. anisetum and P. flabellifolia. The percent maximal response produced by most anethole-containing oils was 30-50%. Fruits of P. isaurica and P. peucedanifolia were estrogenic in spite of the absence or trace amount of anethole, respectively. This study indicates that the estrogenic activity of Pimpinella oils is not solely due to the presence of anethole. Components other than anethole may be responsible for contributing towards the estrogenic activity. The essential oils from different species varied in their estrogenic potencies (relative potency from 8.3 x 10(-8) to 1.2 x 10(-6) compared to 17 beta-estradiol) and among the different plant parts, the fruit oils of most species were estrogenic followed by the aerial parts without fruits and the root oils and their EC50 values varied from 45 micrograms/mL to 650 micrograms/mL.