In the introduction the heuristic basis of neuroendocrinology and the relationship to current concepts in biological psychiatry is analyzed. Various neuroendocrinological approaches to the study of depressive and schizophrenic disorders are then exemplified by the discussion of selected papers. In contrast to studies in schizophrenic patients abnormal findings have been found, by several research approaches, in endogenous-depressive patients. These findings are consistent with the hypothesis of a disfunction of biogenic amines in endogenous depression; however, considering the neuroendocrinological methodology at hand these findings are not conclusive.