The modern quality field in medicine is about one-third of a century old. The purpose of this paper is to summarize what we know about quality of care and indicate what we can do to improve quality of care in the next century. We assert that quality can be measured, that quality of care varies enormously, that improving quality of care is difficult, that financial incentives directed at the health system level have little effect on quality, and that we lack a publicly available tool kit to assess quality. To improve quality of care we will need adequate data and that will require patients to provide information about what happened to them and to allow people to abstract their medical records. It also will require that physicians provide patient information when asked. We also need a strategy to measure quality and then report the results and we need to place in the public domain tool kits that can be used by physicians, administrators, and patient groups to assess and improve quality. Each country should have a national quality report, based on standardized comprehensive and scientifically valid measures, which describes the country's progress in improving quality of care. We can act now. For the 70–100 procedures that dominate what physicians do, we should have a computer-based, prospective system to ensure that physicians ask patients the questions required to decide whether to do the procedure. The patient should verify the responses. Answers from patients should be combined with test results and other information obtained from the patient's physician to produce an assessment of the procedure's appropriateness and necessity. Advanced tools to assess quality, based on data from the patient and medical records, are also currently being developed. These tools could be used to comprehensively assess the quality of primary care across multiple conditions at the country, regional, and medical group level.