Ever since accountability reforms were folded into the aid sector in the 1990s, humanitarian organizations and the larger relief system have developed and improved their ability to evaluate the impact of their work. Relief organizations have, in general, found it easier to measure the impact of their interventions in relation to material needs than activities geared to enhancing protection. For this reason, this scoping study asks “what works in protection and how do we know?” Three related questions are discussed in the following order. The first is how to define humanitarian and human rights protection. The second is how to define success for different types of humanitarian and human rights protection interventions. The third question is how to measure the impact of different protection-oriented interventions.