Monoamine oxidase inhibitors are effective in the treatment of panic attacks. Phenelzine has been used most often with good effect and is regarded by some as the treatment of first choice for panic disorders. Nevertheless the potential dangers of the use of non-specific MAOIs are well recognised and there is a need for safer drugs. The efficacy of specific MAO inhibitors such as moclobemide (MAO-A) and deprenyl (MAO-B) are yet to be investigated. The activity of the enzyme MAO in blood platelet (MAO-B) has been extensively studied. A review of early findings of elevated MAO activity suggests a number of reasons why the data should be interpreted with caution. Recent studies do not support the earlier findings and suggest no difference in platelet MAO activity between patients and controls. Similarly studies of the endogenous MAO inhibitor, tribulin, suggest that the output in panic disorder patients is similar to that of controls. Studies of the effectiveness of specific MAOIs in panic attacks are warranted as are further studies of the biochemical aetiology.