A liquid chromatography-negative ion electrospray ionization-tandem mass spectrometry (LC-ESI--MS/MS) method was developed for the simultaneous analysis of endocrine disruptive chemicals including bisphenol A, 4-octylphenol, 4-nonylphenol, diethylstilbestrol, 17-β-estradiol, estriol, estrone, 17-α-ethinylestradiol, prednisone and prednisolone. Mass spectrometric detection of these target analytes is sensitive to the presence of additives in the mobile phase as well as those used in the sample preparation steps. To avoid issues with reduced mass spectrometry sensitivity, the sample preparation involved elution of the target analytes from the solid-phase sorbent with acetonitrile, drying, and reconstitution with methanol, water, and 2-propanol. Recoveries for all the analytes were from 82.4 to 112%. The detection limits for bisphenol A, octylphenol and nonylphenol using LC-ESI--MS/MS were 1-2 ng/L and for diethylstilbestrol, 17-β-estradiol, estriol, estrone, 17-α-ethinylestradiol, prednisone, and prednisolone were 1-10 ng/L. Mass spectrometric signal suppression was moderate to severe for all analytes except diethylstibestrol. Standard addition calibration was used for quantitation of the target analytes at five wastewater treatment plants in Saskatchewan. Estriol was detected in all the raw wastewater samples with concentrations from 20.4 to 285 ng/L. Estrone and 17-β estradiol were detected in 83% and 67% of the raw wastewater samples at concentrations ranging from 31 to 157 ng/L, and 14 to 100 ng/L, respectively. Concentrations of estrone and 17-β estradiol were higher in raw wastewater than predicted from excretion estimation based on population, indicating non-domestic contribution. In raw wastewater, the concentration of 4-octylphenol was from 127 to 318 ng/L (detected in 33% of raw wastewater samples), and the concentration of 4- nonylphenol was 50 ± 15 ng/L (detected in one location). Bisphenol A was detected in 100% of the raw wastewater samples with concentrations from 133 to 645 ng/L. The concentration of prednisone in raw wastewater was 302 ± 76 ng/L (detected 66%), while prednisolone, which is a metabolite of prednisone, was detected in one raw wastewater sample at 18 ± 1 ng/L. The wastewater treatment process was efficient in the removal of natural estrogens and prednisone with percentage removal of 80-100%, and for BPA generally from 56-100%. The removal efficiency of 4-nonylphenol and prednisolone were very low.