Melancholia is a classical episodic depressive disorder that combines mood, psychomotor, cognitive and vegetative components with high suicide risk. In the present psychiatric classification it is buried as a modifier in both bipolar and unipolar depressions. It is hardly used to characterise patients in the clinic or research. The syndrome is frequently recognised in delusional and agitated depression, and in the elderly. Cortisol or sleep EEG abnormalities are prognostically helpful. Melancholia is particularly responsive to tricyclic antidepressants and electroconvulsive therapy but not to selective serotonin reuptake inhibitors or psychotherapy. Recognising melancholia as a distinct disorder improves clinical care and research.