The hemodynamic response to seizure has long been a topic for discussion in association with the neuronal damage resulting from convulsion. Electroconvulsive therapy (ECT) is an appropriate clinical model for the investigation of the cerebral physiology of seizure. In this study, we monitored the oxygenation state of brain tissue using near infrared (NIR) spectrophotometry, and flow velocity at the middle cerebral artery (MCA) using transcranial Doppler ultrasonography (tc-Doppler) in ninety cases where flow velocity at the middle cerebral artery (MCA) using transcranial Doppler ultrasonography (tc-Doppler) in ninety cases where ECT was prescribed to patients suffering from endogenous depression. Under general anesthesia with thiopental and succinyl choline, an electrical current was applied bilaterally at the minimal energy level. Throughout the therapy, end-tidal CO2 tension was maintained at 30-35 mmHg, and the SpO2 value was maintained above 98% by manual ventilation assistance. The total- and oxy-hemoglobin contents in the brain were reduced during the electrical shock, and then recovered to the pre-shock value (total-hemoglobin; 44.13 +/- 12.88 s after the shock, oxy-hemoglobin; 88.62 +/- 11.69 s after the shock). Subsequently, these values further increased beyond the preshock value. On the other hand, the deoxy-hemoglobin content increased for 90.73 +/- 15.88 s during and after the electrical shock, and decreased afterward. Reduction of cytochrome aa3 began 3.04 +/- 0.51 s after the electrical shock, and this was reoxygenated at 171.88 +/- 12.95 s after the shock.(ABSTRACT TRUNCATED AT 250 WORDS)