From the literature review and our own data the addition of Sleep Deprivation (SD) to anti-depressant therapy increases the response-rate. Evaluation of 35 patients with unipolar (vital) depression who received once a week sleep deprivation in combination with Clomipramine indicates that responders tend to show diurnal variations in symptoms, a family history of affective illness and an age younger than 70 years. Seventeen out of 21 patients who underget DST failed to suppress plasma cortisol levels. Normalisation of the weekly repeated DST was associated with a therapeutic response to sleep deprivations and clomipramine. Even though a failure to suppress cortisol levels did not separate Responders from Non-Responders to SD. Therapeutic failures following SD did respond to subsequent ECT treatment (N= 2). The data indicate that the DST can be helpful in non-suppressors to evaluate the duration of weekly sleep deprivation treatment.