Accidental subdural block is one of the rare complications of epidural anesthesia and can lead to a life threatening condition. A healthy 40 year old woman underwent cesarean section under the diagnosis of placenta previa. Single epidural puncture was performed at L3-4 interspace without difficulty. A test dose of 3ml of 1.5% lidocaine was injected without adverse effects. However, hypotension(80/40) and loss of pain sensation up to the level of C4 were devloped in 5 min. after injection of 25 ml of 1.5% lidocaine with 50ug fentanyl and 2.5ml of 8.4% sodium bicarbonate. She complained of dyspnea without change of SpO2 and difficulty of phonation about 15min. after injetion. And then, She was lethargic, but was able to open eyes with verbal communication. She was fully recovered in 180 minutes after epidural injection. Such extensive block might be caused by subdural administration of the drugs even if it was not confirmed radiologically.