Abstract This paper presents a critical analysis of the environmental responses to the releases of radionuclides and metals from the uranium mining and milling facilities of Poços de Caldas into surface waters. An evaluation of groundwater contamination due to the migration of seepage water from the tailing dam was also performed. The study was based on monitoring data. It is shown that tailing effluent is the most important source of Mn and sulfate to the aquatic environment, while acid mine and waste rock drainage were found to be the main sources of 226Ra, 238U, Al, and Fe. Results from groundwater under the tailing dam showed only sulfate contamination.