The role of norepinephrine in affective disorders is supported by the following data. There is a decrease of activity of the noradrenergic system in depressive patients, evaluated by: --a decrease of the metabolism of noradrenaline; --an hyperreactivity of adrenergic receptors; --a decrease of the secretion of some hormones (melatonine, renine, corticosteroides) the liberation of which is mediated by stimulation of adrenoreceptors. The well recognized antidepressant drugs are able to activate by different mechanisms the noradrenergic system. Reciprocally, drugs well known to stimulate noradrenergic system are able to increase mood. Complementarily, antimaniac drugs are adrenolytic and adrenolytic drugs are antimaniac and depressogenic.