The presence of microconstituents in effluents from municipal wastewater treatment plants (WWTPs) and their receiving waters has attracted considerable recent attention. This review summarizes the state of the science on the removal of bisphenol A (BPA) by WWTPs and presents evidence that the compound should be effectively removed in well-operated activated sludge systems. The biological treatment of BPA has been extensively studied in laboratory, pilot, and full-scale municipal WWTPs. Although removal efficiencies varied, the average of the reported removal efficiencies for BPA in full-scale facilities was 84%. Mass balance studies conducted in the laboratory with 14C-labeled BPA and studies of full-scale facilities show that biodegradation is the dominant removal process, consistent with the fact that BPA is readily degradable and able to support microbial growth. Many of the plants were able to reduce BPA concentrations in the wastewater effluent to significantly less than 1 mg/L. This review examines operating parameters important for optimizing and sustaining the performance of wastewater treatment systems including solids residence time (SRT), which proved to be the most critical. The weight of evidence suggests the optimum SRT needs to be approximately 10 days to ensure high treatment efficiencies. Other optimum operating conditions include maintaining dissolved oxygen concentrations of greater than or equal to 2.0 mg/L, elevating the SRT during periods of low temperature, and implementing step-feed control during storm-induced high flow conditions to avoid the washout of biomass. Water Environ. Res., 83, 650 (2011).