This chapter describes the effects on sleep architecture of psychotropic drugs. It discusses the effects of drugs prescribed as hypnotics or used as hypnotics for their sedative potency as well as the effects of those prescribed for common neuropsychiatric conditions, such as depression and dementia, and that have unintended effects on sleep. The chapter provides the effects on sleep EEG of drugs classified as sedatives or hypnotics as well as those of antidepressant and antidementia drugs. Drugs acting on the benzodiazepine site of the GABAA receptor are the most commonly prescribed drugs for the pharmacological treatment of insomnia. It is thought that neuronal excitability is controlled by these extrasynaptic receptors and it has been suggested that tonic inhibition may be the preferred target for new sedative-hypnotic drugs. The well-documented effects of psychotropic drugs on sleep architecture in the elderly are those of hypnotic drugs.