What should you do when you find out that someone firmly disagrees with you on some claim P? How much should your confidence in your beliefs be shaken when you learn that others, perhaps so-called “epistemic peers” who seem to be as qualified as you are to assess some piece of evidence, hold beliefs contrary to yours? How should you react and update your beliefs (or degrees of) about a certain proposition when you discover that someone else—who is reliable as you are on such matter—disagrees with you? Generally, how your beliefs should be affected by knowing the opinions of others? The cluster of questions stated above refers to an issue which has not attracted much serious attention in mainstream philosophy until recently, namely the puzzle of “peer disagreement”. There are several different answers to these questions now in the literature, and the aim of this article is to characterize them and describe the different motivations that aim philosophers to defend contrasting responses to the problem of “peer disagreement”.