To treat psychiatric symptoms associated with hyperthyroidism, we administered electroconvulsive therapy (ECT) to a patient with Basedow's disease. After unsuccessful treatment with an oral antithyroid drug, neuroleptics, and mood stabilizer, the patient recovered completely after three ECTs and did not relapse in the 40-day follow-up period. Although hyperthyroidism has been considered to induce psychiatric symptoms by enhancement of the sensitivity and turnover in catecholaminergic neurotransmission, we suggest another possible mechanism, involving translational and activational regulation of functional proteins in the brain.