There has been increasing concern about the impact of environmental compounds with hormone-like action on human development and reproductive health over the past decades. An alternative but neglected source of hormone action that may be considered in this connection is hormone residues in meat from husbandry animals treated with sex steroid hormones for growth promotion. Treatment of cattle with naturally occurring or synthetic sex hormones may enhance lean muscle growth and improve feed efficiency and is therefore a very cost effective procedure for cattle producers who have used it for decades in some Western countries, including the USA and Canada. The Joint Food and Agricultural Organisation/World Health Organisation (FAO/WHO) expert committee on food additives (JECFA) and the US Food and Drug Administration (FDA) considered, in 1988, that the residues found in meat from treated animals were safe for the consumers. We have re-evaluated the JECFA conclusions regarding the safety of estradiol residues in meat in the light of recent scientific data, with special emphasis on estradiol levels in prepubertal children. These levels are needed for estimates of the normal daily production rates of estradiol in children, who may be particularly sensitive to low levels of estradiol. In our opinion, the conclusions by JECFA concerning the safety of hormone residues in meat seem to be based on uncertain assumptions and inadequate scientific data. Our concerns can be summarized as follows. 1) The data on residue levels in meat were based on studies performed in the 1970's and 1980's using radioimmunoassay (RIA) methods available at the time. The sensitivity of the methods was generally inadequate to measure precisely the low levels found in animal tissues, and considerable variation between different RIA methods for measuring steroids exists. Therefore the reported residue levels may be subject to considerable uncertainty. 2) Only limited information on the levels of the various metabolites of the steroids was given despite the fact that metabolites also may have biological activity. 3) Reliable data on daily production rates of steroid hormones were and are still lacking in healthy prepubertal children. This lack is crucial as previous guidelines regarding acceptable levels of steroid residues in edible animal tissues have been based on very questionable estimates of production rates in children. Thus, even today the US FDA bases its guidelines on the presumably highly overestimated production rates in prepubertal children given in the JECFA 1988 report. 4) The possible biological significance of very low levels of estradiol is neglected. In conclusion, based on our current knowledge possible adverse effects on human health by consumption of meat from hormone-treated animals cannot be excluded.