The drugs discussed in this chapter have the common pharmacologic characteristic of being central nervous system (CNS) depressants, and they are capable of inducing various clinical responses, including relief of anxiety, sedative-hypnotic effects, and centrally acting muscle relaxation. Although all such drugs induce CNS impairment, drugs in certain categories have some degree of selectivity that determines their therapeutic indications in medical and dental practice. The ability of these agents to induce sedation, hypnosis, anxiolysis, or muscle relaxation selectively is limited, however, and significant overlap in the clinical indications for these drugs occurs. Pharmacokinetic differences and differences in mechanisms of action often distinguish these agents. The multiple actions and uses of these agents are also discussed in other chapters addressing anticonvulsants.