In this chapter, we examine some of the pharmacological properties of benzodiazepines, barbiturates, and other sedative-hypnotic compounds. Sedative drugs moderate excitement, decrease activity, and induce calmness, whereas hypnotic drugs produce drowsiness and facilitate the onset and maintenance of a state that resembles normal sleep in its electroencephalographic characteristics. Although these agents are central nervous system (CNS) depressants, they usually produce therapeutic effects at doses that are far lower than those that cause coma and generalized depression of the CNS.