ECT is the most powerful therapeutic tool in the treatment of acute mood episodes. However, data on the efficacy and safety of ECT in the long term management of affective disorders is lacking, despite overwhelming rates of chronicity and/or frequent relapses among patients with unipolar and bipolar depression. In this presentation we will review the data of the ECT unit of Hospital de Santa Maria, Lisboa, on maintenace ECT (m-ECT) in these patients. We compare intra and inter-individual evolution prior and after the institution of m-ECT. Considering the number of hospital admissions, mood symptoms and other parameters, our data support the use of this technique as a prophylatic approach for patients with mood disorders and a previous good response to ECT in the acute phase of disease.