A medical consensus conference on depression was held in Copenhagen, Denmark, on March 1–3, 1999. The consensus panel addressed the following questions: a) When does dejection constitute depression? b) What do we know about the causes of depression? c) How frequent is depression among different sections of the population? d) Which forms of treatment are available? e) Can several forms of treatment be combined with advantageous results? f) What happens if treatment is not received? g) Should the present organization of efforts be changed? h) What are the costs of depression and treatment of depression? i) Are there areas of research that should be enhanced?