Propofol is often used as an anesthetic agent for electroconvulsive therapy (ECT). The purpose of our study was to compare the dose of propofol in valproateusing patients with valproate free patients. In an open study, 17 patients with bipolar affective disorder manic episode who were to be treated with valproate and ECT combination, compared with 16 manic episode patients who were to be treated with ECT but not valproate. Two groups were compared on the basis of electroencephalography-registered seizure duration and propofol dosage required to induce anesthesia. Valproate, as compared with valproate free group, results in a decrease in propofol dose necessary to induce anesthesia. In valproate group, seizure duration was significantly shorter than valproate free group. In recent studies during the ECT of patients with schizophrenia, propofol was shown to possess significant seizure-shortening properties. When the clinician needs to prolong seizure length in patients under valproate treatment, interruption of valproate treatment or using an anesthetic agent other than propofol should be considered. The results suggest that valproate reduces the dose of propofol required for anesthesia during ECT treatment in patients with bipolar affective disorder manic episode. Although propofol is a safe and efficacious anesthetic for ECT treatment, lower doses of propofol should be used to induce anesthesia for patients under valproate treatment