Theories of cognition frequently assume the existence of inhibitory mechanisms that deactivate mental representations. Justifying this assumption is difficult because cognitive effects thought to reflect inhibition can often be explained without recourse to inhibitory processes. This article addresses the uncertain status of cognitive inhibitory mechanisms, focusing on their function in memory retrieval. On the basis of a novel form of forgetting reported herein, it is shown that classical associative theories of interference are insufficient as accounts of forgetting and that inhibitory processes must be at work. It is argued that inhibitory processes are used to resolve computational problems of selection common to memory retrieval and selective attention and that retrieval is best regarded as conceptually focused selective attention.