Since the early 2000s, oil and natural gas production in the United States have been transformed through technological innovation. Hydraulic fracturing, combined with advanced directional drilling techniques, made it possible to economically extract oil and gas resources previously inaccessible. The resulting surge in production increased domestic energy supplies and brought economic benefits to many areas of the United States. The growth in domestic oil and gas production also raised concerns about potential impacts to human health and the environment, including potential effects on the quality and quantity of drinking water resources. Some residents living close to oil and gas production wells have investigated changes in the quality of drinking water and assert that hydraulic fracturing is responsible for these changes. Other concerns include competition for water between hydraulic fracturing activities and other water users, especially in areas of the country experiencing drought, and the disposal of wastewater generated from hydraulic fracturing. This investigation synthesizes available scientific literature and data to assess the potential for hydraulic fracturing for oil and gas to change the quality or quantity of drinking water resources and identifies factors affecting the frequency or severity of potential changes. This investigation can be used by federal, tribal, state, and local officials; industry; and the public to better understand and address any vulnerabilities of drinking water resources to hydraulic fracturing activities.