Recently, considerable attention has been focused on certain environmental contaminants, endocrine disruptors, of industrial origin that may mimic the action of estrogen. Oral contraceptives containing ethynylestradiol, a synthetic estrogen, have been suspected to have adverse environmental effects since prenatal exposure to diethylstilbestrol, another synthetic estrogen, was reported to be associated with clear cell adenocarcinoma of the vagina in female offspring. In terms of magnitude and extent, such exposures to synthetic estrogens are now considered virtually insignificant compared with the secretion and excretion of natural estrogens from humans. However, as is the case with all other chemicals, continuous and rational risk assessment and risk management of these synthetic estrogens must be made.