Drinking water disinfection by-products (DBPs) are an unintended consequence of using chemical disinfectants to kill harmful pathogens in water. DBPs are formed by the reaction of disinfectants with naturally occurring organic matter, bromide, and iodide, as well as from anthropogenic pollutants, such as pharmaceuticals and pesticides. DBPs are one of a small handful of environmental contaminants that have been definitively linked to adverse human health effects in epidemiologic studies. Several DBPs, such as trihalomethanes (THMs), haloacetic acids (HAAs), bromate, and chlorite, are regulated in the U.S. and in other countries, but other “emerging” DBPs, such as iodo-acids, halobenzoquinones, halonitromethanes, haloamides, halofuranones, and nitrosamines are not widely regulated. This presentation will provide a state-of-the-science overview of the formation of DBPs, new research on determining the important drivers of toxicity in drinking water, and promising solutions for improving the safety of drinking water.