Americans are both undertreated and overtreated in a health care system that wastes up to $1 trillion a year and delivers profoundly uneven quality: Current estimates indicate that preventable medical errors are the third leading cause of death in the United States. Fifty-eight percent of patients referred to Virginia Mason, our medical center in Seattle, for back surgery would be more appropriately treated without an operation. Tens of millions of Americans, most with health care insurance, have never had appropriate screening for colon cancer. Electronic medical records can help correct these systemic defects.