Flunitrazepam is a benzodiazepine derivative whose hypnotic effect predominates over the sedative, anxiolytic, muscle-relaxing and anticonvulsant effects characteristic of benzodiazepines. Thus, it is used as a night-time hypnotic and in anaesthesiology: due to the pronounced hypnotic effect it is not appropriate as a daytime sedative. As a hypnotic for insomnia its effect is usually characterised by a very fast onset of action and quiet sleep without interruptions. On the morning after a hypnotic dose some residual psychomotor impairment does occur, which is comparable to that with usual doses of nitrazepam or flurazepam, but clinically apparent 'hangover' occurs infrequently. There is no pronounced cumulative effect with chronic use. In anaesthesiology it has proven to be useful as a hypnotic on the night before operation, as an oral, intramuscular or intravenous premedication, in induction and as a supplement to other anaesthetics. Its sedative and amnesic properties can also be beneficial in intensive care patients. Much of the usefulness of flunitrazepam in anaesthesia relates to its synergistic effect with other anaesthetics, to its effective amnesic action and its acceptable effects on circulation and respiration. Possible drawbacks include a somewhat unusual course of induction (when used for this purpose) and an often prolonged recovery. Although the safe dosage range is wide with flunitrazepam, its effective application both as a hypnotic for insomnia and in anaesthesiology is dependent upon use of the optimal dosage, and adequate knowledge of its pharmacokinetic properties.