A number of phenomenologic studies have demonstrated the marked heterogeneity of unipolar depressive disorders. We have recently identified a subtype of depression characterized by the presence of irritability and anger attacks. These attacks are sudden spells of anger accompanied by symptoms of autonomic activation such as tachycardia, sweating, flushing, and tightness of the chest. They are experienced by depressed patients as uncharacteristic of them and inappropriate to the situations in which they occur. Approximately one third of depressed outpatients present with anger attacks. Patients with unipolar depression and anger attacks frequently experience significant anxiety and somatic symptoms, and are relatively more likely to meet criteria for avoidant, dependent, borderline, narcissistic, and antisocial personality disorders than depressed patients without these attacks. Anger attacks subside in 53% to 71% of depressed outpatients treated with antidepressants, and the degree of improvement in depressive symptoms after antidepressant treatment is comparable in depressed patients with and without anger attacks. In addition, the rate of emergence of anger attacks after treatment with antidepressants (6%-10%) appears to be lower than the rate with placebo (20%). Finally, antidepressants that affect serotonergic neurotransmission, known to be involved in the modulation of aggressive behavior in animals and humans, may be particularly effective in this subtype of depression, but further studies are needed to support this hypothesis.