A principal objective of health care is to do no harm and to ensure that the benefits of treatment outweigh its deleterious effects. However, unnecessary harm to patients has been part of health care for as long as medicine has been practiced and continues to occur. In recent decades a greater research focus has examined and quantified the extent and costs of patient safety failure across countries and healthcare settings. The increasing complexity of health care also means a higher risk of harm requiring greater vigilance, focus and investment to ensure care is as safe and effective as possible. This report (a) estimates the cost of patient harm, and (b) outlines a strategy for policy makers and healthcare leaders to improve patient safety with limited resources.