Occurrence of five estrogens, including estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2) and bisphenol A (BPA) in water, sediment and biota in Northern Taihu Lake, were investigated and their ecological risk was evaluated. Most of the target estrogens were widely distributed in the eight studied sampling sites, and their levels showed a regional trend of Gong Bay > Meiliang Bay > Zhushan Bay. The average concentrations of E1, E2, E3, EE2 and BPA ranged from 3.86 to 64.4 ng l(-1), 44.3 to 64.1 μg kg(-1) dry weight and 58.6 to 115 μg kg(-1) dry weight in water, sediments and biota, respectively. In most cases, the average concentrations of BPA and E2 were higher than those of other estrogens. E1, E3 and EE2 were found to be accumulated in river snails with bioaccumulation factor values as high as 14,204, 35,327 and 20,127 l kg(-1), respectively. E3 was also considered to be accumulated in clams. The evaluation of environmental risk showed that the occurrence of E2 and EE2 in lakes might pose a high risk to aquatic organisms. These findings provide important information for estrogen control and management in the studied area.