The benzodiazepine-receptors are close by the GABA-receptors. They are found in all areas of the brain, especially in the area of the cortex. The imidazo-benzodiazepine Ro 15-1788 has a high affinity to the receptor without showing any biological activity. The antagonist Ro 15-1788 cancels the sleeping effect, which was produced by benzodiazepines, within 30-60 s. Deep phases of sleep after 4 mg per 70 kg body weight lormetazepam, a dose which was not in clinical use up to now as well as the sleeping effect of 2 mg flunitrazepam per 70 kg body weight and 10-11 mg midazolam per 70 kg body weight are safely antagonized without adverse reactions. According to pharmacodynamic researches by means of EEG and psychometry the half-life period of the antagonist is shorter (1-2 h) than that of the agonist. The clinical application of the antagonist Ro 15-1788 (in patients) is at hand. The control of benzodiazepine-N2O/O2-anaesthesia seems to be guaranteed with the introduction of the antagonist for clinical use.