Syndromes of anxiety include generalized anxiety states, various forms of phobic disorder and panic attacks. It is unclear whether panic attacks are a separate syndrome from anxiety states or a more severe form. Drug-induced states of anxiety should provide useful models of the mechanisms of anxiety and its treatment. High-risk populations might be identifiable. Catecholamine infusions produce marked peripheral changes without fully reproducing the central feelings. Lactate infusions also produce anxiety-like states lacking full credibility. Experience with the benzodiazepine-receptor contragonists, the beta-carbolines, is limited but panic states have been reproduced following their use. Caffeine produces an anxiety state in high dose and some panic states have been induced. The critical evaluation of drug-induced anxiety states is a promising way of elucidating the mechanisms, psychological and physiological, associated with clinical anxiety.