The United States health care industry is the second largest in the world, expending an estimated 479 million metric tons (MMT) of carbon dioxide per year, nearly 8 percent of the country's total emissions. The importance of carbon reduction in health care is slowly being accepted. However, efforts to "green" health care are incomplete since they generally focus on buildings and structures. Yet hospital care and clinical service sectors contribute the most carbon dioxide within the U.S. health care industry, with structures/equipment and pharmaceuticals ranking as the third and fourth highest emitters in the industry. Given the magnitude of health care carbon emissions-and the paucity of attention to the carbon of hospital care and clinical services-this essay identifies overuse of health care as a health threat with serious ethical implications, offers a data-driven action plan for carbon reduction in health care, and provides practical suggestions for more sustainable health care delivery in the United States.