It is often argued that widespread disagreement among epistemic peers in a domain threatens expertise in that domain. This chapter sketches two different conceptions of expertise: the expert-as-authority and the expert-as-advisor models. While it is standard for philosophers to understand expertise as authoritative, such an approach renders the problem posed by widespread peer disagreement intractable. This chapter argues, however, that there are independent reasons to reject both this model of expertise and the central argument offered on its behalf. The chapter then develops an alternative approach—one that understands expertise in terms of advice—that not only avoids the problems afflicting the expert-as-authority model, but also has the resources for a much more satisfying response to the problem of widespread peer disagreement.