This report deals with a series of experimental approaches carried out in clinical studies to attempt to examine the role of amines in relationship to affective state and the mode of action of thymoleptic agents. Attempts have been made to examine enzymes, amines and other metabolites in biological fluids to assess the role of catecholamines and indoleamines in these disorders. Synthesis inhibitors were employed in studies where antidepressant drug-induced remission was initiated and the effect of two inhibitors was assessed on the clinical state. The results are presented and discussed in regard to the significance of the role of serotonin in depressive states and the action of thymoleptic agents.