Abstract
Despite increased advocacy for patient safety and several large-scale programs designed to reduce preventable harm, most notably surgical checklists, recent data evaluating entire health systems suggests that we are no further ahead in improving patient safety and that hospital complications are no less frequent now than in the 1990s. We suggest that the failure to systematically measure patient safety is the reason for our limited pro gress. In addition to defining patient safety outcomes and describing their financial and clinical impact, we argue why the failure to implement patient safety measurement systems has compromised the ability to move the agenda forward. We also present an overview of how patient safety can be assessed and the strengths and weaknesses of each method and comment on some of the consequences created by the absence of a systematic measurement system.