Denunciations are prevalent in authoritarian regimes. But should an autocrat trust these delations? We answer this question in different social situations with the help of a theoretical framework. In our set-up, the autocrat seeks to screen aligned from misaligned agents. Each agent is paired with another agent, either as co-workers, as manager-subordinate, or as service provider-citizen, and has information about the malfeasance of the paired agent. The agent then decides whether to denounce her counterpart to the autocrat. The autocrat then decides whether to conduct investigations to obtain additional evidence and makes a decision whether to repress or not the agents. Our framework provides a novel understanding of denunciation, why and when they work, their frequency, and their consequences.