We report the results of a recent survey of the concentration of natural estrogens (17߭estradiol, 17a-estradiol, estrone, estriol) and the synthetic estrogen, 17a-ethynylestradiol in representative animal wastes and sewage treatment plant (STP) effluents in the Waikato region of New Zealand. Dairy farm effluent samples showed high levels of estradiol (19-1360 ng/L) and its breakdown product estrone (41-3123 ng/L) compared with piggery or goat farm effluents. The combined load for these estrogens (excluding ߠepimer) varied from 60 to > 4000 ng/L. The piggery effluent provided the lowest total estrogen load (46 ng/L), with estrone accounting for nearly 60% of the measured estrogens in this sample. The synthetic analogue, 17a-ethynylestradiol was detected only in one wastewater treatment plant sample, albeit at trace level. An estrogen receptor competitive binding assay was used to test the biological activity of the samples and confirmed that most agricultural waste samples contain high levels of estrogenic compounds. The potential of these wastes to cause endocrine disruption in the receiving ecosystem is unknown at present