This paper proposes a novel theoretical framework to study the features of mass purges in authoritarian regimes. We contend that mass purges are an instrument of top-down accountability meant to motivate and screen a multitude of agents (e.g., single-party members, state bureaucrats). We show that the set of purged agents is well delineated in mild purges, whereas no performance indicator is a guarantee of safety in violent purges. The proportion of purged agents is non-monotonic in the intensity of violence. For the autocrat, increasing the intensity of violence always raises performance, but it improves the selection of subordinates only if violence is low to begin with. Hence, even absent de jure checks, the autocrat is de facto constrained by her subordinates’ strategic behavior. We use historical (including the Soviet purges and the Cultural Revolution) and recent (the Erdogan purge) events to illustrate our key theoretical findings.