Due to the wide margin of safety and their pharmacological properties benzodiazepines are among the most widely used drugs in anaesthesiology and intensive care. Onset, duration and intensity of action depends mainly on their pharmacokinetic characteristics which exhibit some differences between the numerous compounds. All benzodiazepines possess dose-dependently anxiolytic, sedative-hypnotic, muscle relaxant and anticonvulsive properties. Likewise, the profile of side effects is almost identical, because all central actions of the benzodiazepines are based on a common molecular mechanism. CNS-depressant reactions, such as sedation, (hang-over) fatigue, ataxia, impairment of motor coordination and intellectual functions including memory (amnesia!) are most frequent, especially in the elderly if dosage has not been reduced accordingly. Rapid injection of higher doses should be avoided because these drugs (especially midazolam) can suppress ventilation. However, if benzodiazepines are properly used in patient-adjusted dosage they will represent valuable drugs in anaesthesiology and intensive care.