In June 2006, the Institute for Healthcare Improvement (IHI) announced that hospitals participating in their 100,000 Lives Campaign saved an estimated 122,300 lives. In an invited commentary, Drs. Robert Wachter and Peter Pronovost critically analyze the campaign, the interventions promoted, and the "lives saved" estimates. While applauding IHI's remarkable efforts in stimulating the system to improve quality and safety, the authors raise concerns about the evidence base behind the recommended interventions (particularly rapid response teams) and the methodology underlying the lives saved estimate. Even as they critique some of the science, they suggest that the campaign's success in engaging so many (approximately 3,000) hospitals may hold lessons for other organizations seeking to promote improved health care. IHI President Dr. Don Berwick and colleagues respond to the commentary (available via the link below), welcoming the critical appraisal while defending both the interventions and the methods used in reporting the campaign's outcomes. Wachter and Pronovost offer further comments in response.