Benzodiazepines are used as hypnotics, tranquilizers, anticonvulsants or muscle relaxants. Antidepressants are also used for the treatment of psychiatric disorders such as depression. These also possess tranquilizing properties. Many of the benzodiazepines are used in combination with antidepressants in the management of depression as they also show antidepressant activity in addition to the pharmacological action common to benzodiazepines. For the medical treatment of depression and neurosis, the concomitant administration of tricyclic antidepressants and benzodiazepines is widely used. Both drugs rank as the most frequently prescribed class of drugs, and therefore their monitoring in biological fluids is quite important taking into account that they can produce dangerous biochemical imbalances in toxic doses. Efficient toxicological analysis is the basis of a competent toxicological judgement and consultation in clinical and forensic toxicology. In contrast to forensic toxicology, clinical toxicology has to deliver its result within a short time span. In this concern LC-DAD/UV is the method of choice for the quantification of drugs and their metabolites in biologic fluids.