One of the main problems in the therapy of depression is the lack of markers indicating: the acute state of depression, the drug resistance or helpful in foreseeing the therapeutic response. This article is a literature review of current knowledge concerning laboratory markers of depression. Authors discussed the results of clinical trials investigating the immunological and biochemical disturbances (changes in serum level of trace elements, aminoacids and lipids) concomitant with depression. Hormonal tests (e.g. dexamethasone suppression test, fenfl uramine challenge test, TRH stimulation test, assay of serum and CSF level of steroid hormons), platelet and leukocyte markers were also presented.