US health care is in ferment. Private entities are merging, aligning, and coordinating in a wide array of configurations. At the same time, there is a great deal of policy change. This includes the federal government’s Affordable Care Act, as well as actions by Medicare, state legislatures, and state agencies. The health system is built upon markets, which determine how (and how well) goods and services are delivered to consumers, so it is critical that these markets work as well as possible. As the primary federal antitrust enforcement agencies, the Federal Trade Commission and the Department of Justice are charged with ensuring that health care markets operate well, but they are not alone. The functioning of health care markets is also profoundly affected by other parts of the federal government (notably the Centers for Medicare and Medicaid Services) and by state legislation and regulation. In this current period of such dynamic change, it is particularly important for the antitrust agencies to continue and enhance their communication and coordination with other government agencies as well as to maintain vigilant antitrust enforcement and consumer protection in health care markets.