Experimental investigations of hypnotic amnesia began in the early twentieth century. Much of the early experimental work lacked an objective, standardized measure of responsiveness to hypnotic suggestions. This chapter reviews the status of knowledge and thinking about hypnotic amnesia and presents the experimental evidence supporting these conclusions. The survey of the literature should be considered representative, rather than exhaustive. The chapter discusses the definition of hypnotic amnesia and the means devised to measure it. It describes representative studies investigating each type, including the evidence for their occurrence as well as their relationship to one another. The chapter also discusses the variables which have been found to give rise to and affect the nature of hypnotic amnesia. It provides various mechanisms that have been proposed to theoretically explain amnesia. The chapter also presents the concepts of function ablation, repression, dissociation, and retrieval disruption.