Fluoxetine inhibits serotonin uptake selectively and increases extracellular concentrations of serotonin in brain regions. The enhanced serotonergic neurotransmission resulting from increased action of that extracellular serotonin on postsynaptic receptors on target neurons results in various functional changes, reflecting the wide distribution of serotonin nerve terminals in brain regions that regulate numerous physiological functions. One consequence of fluoxetine administration in animals is a reduction of aggressive behavior, consistent with a larger body of data implicating serotonin as an important neurotransmitter modulator of aggression. In humans, preliminary data suggest that fluoxetine may also decrease aggressive behavior and feelings of anger or hostility. Further investigation of the potential usefulness of fluoxetine and other drugs that increase serotonergic function as a means of reducing anger, hostility, and aggressive behavior seems warranted.