BACKGROUND: In Denmark, over 2500 people are in psychiatric treatment in forensic mental health services at any one time, most suffering from schizophrenia. Many of them have illnesses that are resistant to medication. There is evidence of the effectiveness of electroconvulsive therapy (ECT) for schizophrenia, but not explicitly for this complex forensic group. AIMS: The aim of this study was to describe the outcome of using ECT as augmentation therapy in a cohort of forensic psychiatric patients with schizophrenia who were failing to respond to antipsychotic medication. METHODS: In one university-based psychiatric clinic, data were extracted from the medical records of all patients treated with ECT during a 6-year period. Fifty-nine of these patients were diagnosed within the schizophrenia spectrum and eight were in specialist forensic hospital services. RESULTS: The mean duration of illness for the forensic cohort was 16¿years (range 3-33¿years), with the index episode having lasted a mean of 34¿months (3¿weeks to 8¿years) in spite of treatment with at least two antipsychotic drugs. Psychotic symptoms were accompanied by seriously assaultive behaviour in all cases. All but one of these patients had an excellent or good symptomatic and behavioural response to ECT. Half (four) went on to maintenance ECT. No adverse effects were documented. CONCLUSION: ECT is rarely used in specialist secure services, but should not be forgotten as a treatment that may enable medication-resistant, assaultive psychotic patients to progress safely out to the community. Copyright © 2011 John Wiley & Sons, Ltd.