Since ancient times the influence of chronobiological factors on the pathogenesis, course, and treatment of depression has been well known. Amongst antidepressive treatment strategies two are based on chronobiological knowledge: therapeutic sleep deprivation, which exerts a rapid and dramatic, albeit usually short-lasting, improvement of mood in the majority of patients with major depressive disorder, and light therapy with full-spectrum bright light. About sixty percent of all depressed patients improve after a single night of total or partial sleep deprivation. It has been shown that a combination of pharmacotherapy with antidepressants and sleep deprivation is superior to pharmacotherapy alone. Moreover, sleep deprivation has proved to hasten the onset of action of antidepressant medication and repeated sleep deprivation can also be an efficient treatment strategy in drug refractory depression. Light therapy with bright artificial light is especially beneficial in patients with a fall/winter pattern of depressive symptomatology that has been termed seasonal affective disorder. Similar to sleep deprivation, bright light therapy is characterized by a fast onset of antidepressant action and by the exertion of additive properties to antidepressive medication. Bright light therapy, beginning in the morning after partial sleep deprivation, is able to prevent the depressive relapse after the next night of sleep in sleep deprivation responders.