Although there is little public discussion of the problem, disease outbreaks caused by contaminated water occur regularly. Researchers estimate that, including unreported cases, between 4 and 33 million waterborne gastrointestinal illnesses occur each year in the United States. Global warming is projected to increase the risk of more frequent and more widespread outbreaks of waterborne illnesses, due to higher temperatures and more severe weather events. To help prevent increased occurrence of water-related illnesses, the CDC should improve surveillance of waterborne disease outbreaks, the Environmental Protection Agency (EPA) should improve water quality regulations, and Congress should act to limit emissions of global warming pollutants. We need to act now to protect public health today while preparing for the impacts of climate change.