The purpose of the present paper was to study the effect of continuation electroconvulsive therapy (ECT) on the prevention of relapse in middle-aged and elderly patients with intractable catatonic schizophrenia. It was found that continuation ECT is efficacious to sustain remission for patients who suffer relapse after response to acute ECT despite continuation neuroleptics. However, three patients suffered relapse during continuation ECT, therefore the effect of adjusting the frequency of continuation ECT and maintenance ECT was investigated in these patients with catatonic schizophrenia who relapsed during continuation ECT. These patients with DSM-IV catatonic schizophrenia who relapsed during continuation ECT were treated with more frequent continuation ECT and subsequent maintenance ECT after response to acute ECT. The patients' Brief Psychiatric Rating Scale (BPRS) scores were prospectively evaluated until relapse. Patients were considered to be relapsers if they had a BPRS score >or=37 for 3 consecutive days. The three patients with catatonic schizophrenia who relapsed during continuation ECT were treated successfully with more frequent continuation ECT and subsequent maintenance ECT. No patient experienced a severe adverse effect from continuation or maintenance ECT. More frequent continuation ECT and maintenance ECT deserves consideration in middle-aged and elderly patients with intractable catatonic schizophrenia who suffer relapse during continuation ECT. Large-scale systematic studies are warranted to investigate the optimum use of continuation and maintenance ECT in patients with catatonic schizophrenia.