Endocrine disrupting compounds (EDCs) have attracted the attention of the scientific community because of the effects of EDCs on aquatic fauna and the potential threat they pose to human health. There are a handful of papers on the monitoring of EDCs in Brazilian surface waters, hence this research was aimed at assessing, by using liquid chromatography coupled to mass spectrometry (LC-MS), the presence of 17 beta-estradiol, 17 alpha-ethynylestradiol and 4-nonylphenol in surface waters used for supplying the Belo Horizonte Metropolitan Area, Minas Gerais state, Brazil. The one-year monitoring period of three water sources showed that 4-nonylphenol was detected in all samples in a concentration range of 44 to 1918 ng L(-1), whilst the natural and synthetic estradiols were hardly detected (only in approximately 15% of samples) and always in low concentrations (2 to 54 ng L(-1)). Samples of partially treated water, collected in three water treatment plants before the chlorination step, showed that the steps of prechlorination, flocculation-sedimentation and sand filtration did not efficiently remove the EDCs studied.