Methods: This is a pilot double blind, placebo controlled and randomized study to assess electroconvulsive therapy efficacy as augmenting strategy to clozapine in super-refractory schizophrenia. The ECT treatment will be delivered with either a MECTA SPECTRUM 5000Q or 4000Q device, and the procedure is under general anesthesia and monitorization, after informed consent. The Hospital will follow national protocols and regulations on ECT. Sham ECT consists in habitual patient preparation and sedation, without stimulation. Patients that fit inclusion criteria will have their clozapine blood levels dosed and undergo structured assessments at baseline, after 6 treatments and at the end of the cycle of 12 ECT sessions (thrice a week protocol). The assessments will be based on CGI (Clinical Global Impression) and PANSS (Positive and Negative Syndrome Scale) scales. All medication will be maintained, except lithium carbonate.