The present study investigated relationships between carbamazepine dose, carbamazepine (Tégrétol®) and 10, 11-epoxide-carbamazepine plasma concentrations, and clinical responses to carbamazepine treatment in Tunisian bipolar patients. Twelve patients with bipolar II disorder were diagnosed as having an affective disorder. These patients recruited for this study were treated with carbamazepine for 60 days. Patient health improvement was assessed before and after each cycle of two weeks of carbamazepine therapy, using the Brief Psychiatric Rating Scale (BPRS). Plasma carbamazepine (CBZ) and 10, 11-epoxidecarbamazepine concentrations (CBZ-E) were determined by high-performance liquid chromatography (HPLC). No significant correlations between plasma carbamazepine and clearance-carbamazepine and clinical health improvement among our bipolar patients were found. However, a significant correlation was observed between clinical health improvement given by BPRS scores and 10,11-epoxide-carbamazepine plasma concentration to daily carbamazepine dose ratio (CBZE/ D). Despite the small sample size of our study, our findings suggest that the carbamazepine therapy response variations observed in our patients may be, in part, explained by the interindividual differences in plasma 10,11-epoxide-carbamazepine concentration to carbamazepine dose ratio (CBZ-E/D). So the CBZ-E/D parameter could be used as a good indicator for adjusting the carbamazepine doseadaptation strategy and consequently for improving the clinical psychopathological state of bipolar patients.