Bees, both commercially managed honey bees and wild bees, play an important role in global food production. In the United States, the value of honey bees only as commercial pollinators in U.S. food production is estimated at about $15 billion to $20 billion annually. The estimated value of other types of insect pollinators, including wild bees, to U.S. food production is not available. Given their importance to food production, many have expressed concern about whether a "pollinator crisis" has been occurring in recent decades. In the United States, commercial migratory beekeepers along the East Coast of the United States began reporting sharp declines in 2006 in their honey bee colonies. The U.S. Department of Agriculture (USDA) reports that overwinter colony losses from 2006 to 2011 averaged more than 32% annually. This issue remained legislatively active in the 110th Congress and resulted in increased funding for pollinator research, among other types of farm program support, as part of the 2008 farm bill (P.L. 110-246). Congressional interest in the health of honey bees and other pollinators has continued in the 112th Congress (e.g., H.R. 2381, H.R. 6083, and S. 3240) and may extend into the 113th Congress. This report: Describes changes in managed and wild bee populations, given readily available data and information. It focuses on managed and wild bees only, and excludes other types of pollinators, including other insects, birds, and bats. Data on managed honey bees are limited, and do not provide a comprehensive view of changes in bee populations. Data for wild bee populations are even more limited; Provides a listing of the range of possible factors thought to be negatively affecting managed and wild bee populations. In addition to pesticides, other identified factors include bee pests and diseases, diet and nutrition, genetics, habitat loss and other environmental stressors, and beekeeping management issues, as well as the possibility that bees are being negatively affected by cumulative, multiple exposures and/or the interactive effects of each of these factors; Briefly summarizes readily available scientific research and analysis regarding the potential role of pesticides among the factors affecting the health and wellbeing of bees, as well as the statutory authority and related regulatory activities of the U.S. Environmental Protection Agency (EPA) related to pesticide use. A 2007 report by the National Research Council of the National Academy of Sciences, Status of Pollinators in North America, provides a more detailed scientific context for this report and may be consulted for more in depth understanding about bee health. That study concluded that many factors contribute to pollinator declines in North America, and CRS accedes to that conclusion. Accordingly, the focus of this report on bee exposure to pesticides is not intended to imply that pesticides are any more important in influencing the health and wellness of bees than any of the other identified factors influencing bee health. Pesticides are only one of the many influences on bee health. Because neonicotinoid pesticides have been the focus of concerns in Europe and in the United States, this report briefly describes recent scientific research related to possible effects of exposure to these pesticides on bees. The report concludes with a summary of recent regulatory activity regarding neonicotinoids at EPA, the federal agency charged with assessing risks and regulating U.S. sale and use of pesticides.