A decade ago the Institute of Medicine estimated that 44,000-98,000 preventable deaths occur each year in US hospitals. The leaders of Ascension Health-one of the nation's largest health care delivery networks, with sixty-nine hospitals in twenty states and the District of Columbia-dedicated themselves to preventing equivalent numbers of deaths in their system. In 2003 they set a goal of reducing preventable deaths by 900 each year by 2008. By fiscal year 2010 Ascension Health had reduced preventable deaths by more than 1,500 people annually and, by some calculations, by more than 5,000 people annually, compared to 2004. Ascension Health had also achieved important improvements in preventing birth trauma and reducing rates of pressure ulcers and hospital-acquired infections. The health care system could achieve even greater results by adopting the safety principles used in high-reliability entities such as the nuclear power industry. The adoption of such principles can lead to impressive improvements in health care quality.