Background: Owing to the low therapeutic index of barbiturates, benzodiazepines (BZDs) became popular in this country and worldwide many decades ago for a wide range of conditions. Because of an increased understanding of pharmacology and physiology, the mechanisms of action of many BZDs are now largely understood, and BZDs of varying potency and duration of action have been developed and marketed. Although BZDs have many therapeutic roles and BZD-mediated effects are typically well tolerated in the general population, side effects and toxicity can result in morbidity and mortality for some patients. The elderly; certain subpopulations of patients with lung, liver, or kidney dysfunction; and patients on other classes of medication are especially prone to toxicity. Methods: This review details the present knowledge about BZD mechanisms of action, drug profiles, clinical actions, and potential side effects. In addition, this review describes numerous types of BZD-mediated central nervous system effects. Conclusion: For any patient taking a BZD, the prescribing physician must carefully evaluate the risks and benefits, and higher-risk patients require careful considerations. Clinically appropriate use of BZDs requires prudence and the understanding of pharmacology. © Academic Division of Ochsner Clinic Foundation.