Anxiety states comprise three components, the subjective, the physiological and the behavioural. Anxiety disorders differ from normal anxiety in that cognitive clues inducing the emotion are covert. Anxiety can be induced by a variety of chemical agents, including the catecholamines, caffeine, lactate and some beta-carbolines. Models can be built up from the standpoints of Schachter, Lader and Matthews, and Clark to provide a cohesive theoretical framework for anxiety and panic disorders. Both pharmacological and psychological treatments are effective in these conditions and the model can incorporate the mode of action of these therapies. The ultimate goal is a holistic concept of anxiety combining the bio-psycho-social approaches.