A qualitative description of the amnesia produced by the benzodiazepines in man is presented. The benzodiazepines exert their greatest effects in tests of long-term episodic memory in which they cause a dose-related impairment in the acquisition of new information, do not appear to affect retention and may facilitate retrieval. Benzodiazepines do not appear to impair semantic memory or the acquisition of skills. Although state-dependent learning may be observed with benzodiazepine treatment it is a small effect and cannot account for most of the observed impairments. The amnesia appears to be characteristic of all benzodiazepines and may be related to the sedative action of these compounds but evidence on the latter point is inconclusive. The importance of the amnesic action in a population of clinically anxious outpatients taking benzodiazepines over an extended period remains to be investigated. The benzodiazepines may provide the cognitive psychologist with a useful tool to investigate the mechanisms of normal memory.