Estrogenic potency of water samples from various rivers and wastewater treatment plants (WWTPs) in Shanghai was determined to assess the estrogenic pollution in typical Chinese urban regions. While the estrogenic activity, calculated as estradiol equivalents (EEQs), in surface water was found to be 2.48-41.9 ng/L, it was 47.7-80.1 ng/L in the influents from WWTPs. After treatment (removal rate of 62.3%-83.6%), the EEQ level in effluents was 7.82-24.8 ng/L, which was within the range of the corresponding receiving rivers. Our findings suggest that WWTP effluents may not be the predominate source of potential aquatic estrogenic contamination in Shanghai.