Recent years have seen growing enthusiasm for public engagement in priority-setting. But despite this widespread support, there remains uncertainty both about the precise benefits of public engagement in priority-setting and about how public engagement activities should be structured in order to realize those benefits. The authors aim to move beyond generalizations about the value of public engagement by presenting several distinct rationales for engaging the public in priority-setting. The authors illustrate how these rationales can be achieved in practice using the case study of directly observed therapy for tuberculosis. They then highlight a number of practical challenges involved in implementing engagement activities and offer advice for addressing them. The chapter pays particular attention to challenges that arise in low- and middle-income countries, where efforts to engage the public face unique structural barriers.