Unipolar depression is among the leading causes of invalidity and disability-adjusted life-years. General practitioners frequently encounter patients suffering from depressive syndromes and very often, it's they, who make the initial diagnosis, take care of these patients, eventually prescribe an antidepressant treatment, identify difficult cases and address them to the specialists of mental health. In this article, we present concepts of diagnosis and differential diagnoses of depression, its therapy and the collaboration between the general practitioner and the psychiatrist/psychotherapist.