The central benzodiazepine binding site mediates the therapeutically relevant pharmacologic actions of benzodiazepine agonists, including reducing anxiety, sedation, muscle relaxation, and antagonism of seizure production. Benzodiazepines potentiate the ability of γ-aminobutyric acid (GABA) to promote membrane chloride ion conductance by binding reversibly to a distinct site on the GABAAreceptor complex. Although the role of this central benzodiazepine binding site in mediating the pharmacologic actions of benzodiazepine agonists has been shown conclusively, its participation in an animal's response to stress is less certain. Data are reviewed consistent with an environmental stress-induced modification of the structure and function of the central benzodiazepine binding site. Modifications show brain anatomic regional selectivity. The mechanisms of these modifications include rapid enzyme-mediated phosphorylations of the GABAAreceptor complex and the selective transcription of individual polypeptide subunits. The potential relevance of the data on environmental stress-induced functional modifications of the central benzodiazepine binding site to the development of newer medications and improved understanding of the pathophysiology of stress-related neuropsychiatric disorders is discussed.