The main source of natural estrogens to municipal wastewater is human excretions via urine or feces, thus their concentrations in raw wastewater should show positive linear relationship with their human excretions. This study mainly focused on their concentration relationship in raw wastewater. Based on comparison between chemical analyses and predictions through human excretion rates, the observed concentrations of estriol (E₃) in municipal wastewater were found to be noticeably lower than the predicted values. The main cause for the disparity is that substantial conjugated E₃also exists in raw wastewater. This work suggested that monitoring both E₃and its conjugates is necessary to get more accurate E₃removal performance of wastewater treatment plants (WWTPs).