In the geriatric patient with COPD, incidence of postoperative pulmonary complication is higher than young patient. Therefore, some anesthesiologists preferred spinal anesthesia to general anesthesia for surgery of the perineum, lower extrimities, and pelvic extra peritoneal organs. But, during spinal anesthesia, the same careful observation is requiered as during general anesthesia. We experienced a case of the convulsive seizure at about 1 hour after spinal anesthesia for open prostatectomy in a 76-year-old male patient wit COPD. It was suspected that his convulsive seizure be resulted from hypercapnea combined with hypoxia following upper airway obstruction. This patient was treated successfully by ultrashort acting barbiturate and controlled ventilation.