The first generation monoamine oxidase inhibitors (MAOI's) acted as antidepressants by increasing presynaptic stores of all monoamines and caused both the reaction with tyramine and psychosis. The newer selective, reversible inhibitors of the MAO-A system that are currently undergoing trials aim to act more specifically through noradrenaline and serotonin, and might be expected not to involve the same problems. This article describes a case of psychosis precipitated by the MAO-A inhibitor brofaromine and suggests possible mechanisms to explain it.