Aim: It is reported that clozapine maintenance treatment could be effective in treatment-resistant bipolar patients. The aim of this study is to evaluate the prescription rates of clozapine, features of patients on clozapine prophylaxis and efficacy of clozapine prophylaxis in patients with bipolar disorder. Material and Method: 280 patients with DSM-IV diagnostic criteria for bipolar disorder, type I were included in the study. The patients' medical records and life-charts were reviewed retrospectively and patients who took clozapine for maintenance treatment for at least one year were identified. Results: Twelve of 280 patients (4.8 %) took clozapine for prophylaxis for at least one period during lifetime. Among them 7 patients have only received clozapine, while 5 patients have used combination of clozapine and valproic acid. All of these twelve patients had resistance to at least two different maintenance treatments before clozapine prophylaxis. However, positive results were observed in all of the patients with clozapine prophylaxis. Discussion: These findings suggest that clozapine is regarded as an effective prophylactic choice for treatment of resistant patients with bipolar disorder. Consequently, this study demonstrates effectiveness and safety of clozapine use even in severe patients refractory to various strategies of prophylaxis. Retrospective nature of our study constitutes a limitation. However, when considering limited number of studies on this subject, it may still have a significant contribution. But more comprehensive prospective controlled studies are still needed.