In recent years, the frequency with which patients present with ‘double depression’, i.e. coexisting chronic depression (dysthymia)andacute major depression, has become increasingly evident. A growing research literature demonstrates that patients with double depression are at increased risk for poor outcome, including poor psychosocial functioning, high usage of medical services, high rates of suicide attempts, and increased recurrence of major depression. Furthermore, naturalistic studies have shown that when these patients are treated in the community, they often do not receive adequate antidepressant medication to treat their acute or chronic depressive disorders.In this article, we introduce a typology that is designed to assist clinicians in determining useful strategies in the short and long term treatment of double depression. This differentiates between those patients with double depression who present primarily with acute depression; those presenting primarily with chronic depression (where treatment can focus on the single, more severe disorder, and may be time-limited or episodic): and those presenting with severe acute depressionandsevere chronic depression, in whom lifelong medication is often required. Aggressive treatment is recommended for all patients with double depression, but refined treatment strategies based on depressive typology may help to increase compliance, consolidate therapeutic gains and forestall relapse.A growing psychopharmacology literature shows that several different classes of medication [tricyclic antidepressants, monamine oxidase inhibitors, selective serotonin (5-hydroxytryptamine: 5-HT) reuptake inhibitors and others] are effective in the treatment of double depression, although perhaps somewhat less effective than in the treatment of acute major depression.