Regulations are one of the primary drivers for research on contaminants in drinking water in the United States. Since the original Safe Drinking Water Act (SDWA), enacted in 1974, the United States Environmental Protection Agency (USEPA) has developed a series of drinking water regulations. These regulations are focused on protecting public health. When evaluating available information on whether or not to regulate a constituent in drinking water, USEPA considers available information on health effects and occurrence of the constituent. The authors provide their view of the research needed for these contaminants. For inorganics, more data are needed on perchlorate. For organics, greater treatment and health effects information is warranted for N-nitrosodimethylamine (NDMA), methyl tertiary butyl ether (MTBE) and pharmaceuticals and personal care products. Finally, more research is needed on analytical methods for noroviruses and other emerging pathogens.