Emerging contaminants are those constituents about which we are just beginning to develop the analytical techniques to measure; thus they are "emerging" in awareness, interest, and capability to measure quantitatively. These constituents have most likely been in the environment for decades but we are only now becoming aware of their impact, such as caffeine (when found in groundwater it is an indicator of treated municipal wastewater), artificial sweeteners, and flame retardant chemicals as well as the effects of nanoparticles. What tools should be used and how should the potential for risk be evaluated and addressed? What factors come into play from threat recognition to contaminant confirmation? How can the industry, private sector, and government work together to best address these contaminants?