This chapter discusses the four main reasons to measure outcomes: 1. measuring the change in outcomes tells you how you are doing with respect to providing health care; 2. with outcome data you can identify opportunities for learning and improvement; 3. outcome data give patients and their families critical information about what to expect when they seek care from you or your organization (or, if you work for a payer organization or employer, from the health care providers within your network); and 4. you have an ethical obligation to understand whether the care you provide is helping or harming.