The ethyl ester of β-carboline-3-carboxylic acid (β-CCE) has a high affinity for benzodiazepine receptors and can antagonize some of the pharmacologic actions of benzodiazepines in rodents. Administration of β-CCE (2.5 mg/kg) to chair-adapted, male rhesus monkeys (7–9 kg) elicited a behavioral syndrome characterized by extreme agitation, head and body turning, distress vocalization and other behaviors which might be termed ‘anxious’. Concomitant increases in plasma cortisol, epinephrine, norepinephrine, heart rate, and mean arterial blood pressure were observed. Pretreatment of animals with the benzodiazepine receptor antagonist Ro 15–1788 (5 mg/kg) antagonized the behavioral, endocrine, and somatic changes produced by β-CCE, but did not elicit any significant changes in these parameters when administered alone. Thus, administration of β-CCE to primates may be a reliable and reproducible model of human anxiety and, as much, may prove valuable for studying the postulated role of ‘stress’ or ‘anxiety’ in a variety of human disorders. In toto, these results strongly suggest that benzodiazepine receptors not only mediate the pharmacologic actions of benzodiazepines, but may also subserve both the affective and physiologic expression of anxiety.