OBJECTIVE The aim of this article is to critically review all published studies regarding the efficacy and safety of the concurrent administration of clozapine (CLZ) and electroconvulsive therapy (ECT) in CLZ-resistant schizophrenic or schizoaffective patients. METHODS A MEDLINE search from January 1980 to July 2005 was conducted. RESULTS One open-label trial and 6 case studies were located, comprising 21 schizophrenic and 1 schizo affective patients (12 men and 10 women) with a mean age of 41.9 years. The duration and dosage of CLZ monotherapy before ECT were reported at least 12 weeks and 300 mg/d, respectively, in 10 patients (45.4%). Plasma CLZ levels before ECT were assessed in 12 patients (54.5%), in which only 7 (31.8%) were reported to be higher than 350 ng/mL. The CLZ dosage during ECT ranged from 200 to 900 mg/d (mean, 518.2 +/- 203.3 mg/d). The number of ECT sessions ranged from 2 to 20 (mean, 11.5 +/- 5.4). Application of electrodes was unilateral in 7 patients, bilateral in 10 patients, and mixed in 2 patients. Sixteen patients (72.7%) showed marked improvement whereas 6 patients (27.3%) had moderate, minimal, or no improvement. No predictors of outcome could be isolated. Side effects reported by 5 patients (22.7%) were nausea, tachycardia, hypertension, memory problems, and confusion. Ten patients (45.4%) relapsed during follow-up. Substantial improvement persisted beyond 4 months in only 5 patients (22.7%). CONCLUSIONS Preliminary evidence exists for the safety and short-term efficacy of the concurrent administration of CLZ and ECT in CLZ-resistant schizophrenic or schizoaffective patients.