Acute subdural hematoma is an exceptionally rare, but life-threatening complication of spinal anesthesia. The authors report here on a case of acute subdural hematoma in a 52-year-old male who underwent an arthroscopic knee joint operation under spinal epidural anesthesia due to tearing of the medial meniscus. He complained of headache after surgery. Computed tomography[CT] revealed acute subdural hematoma in the right fronto-tempo-parietal area. The headache progressed in spite of analgesics and bed rest; two weeks later, the CT showed subacute subdural hematoma with a mass effect. The patient improved after surgical decompression. The pathogenesis of subdural hematoma formation after dural puncture is discussed and we briefly review the relevant literature. Prolonged and severe postdural puncture headache[PDPH] should be viewed with suspicion and investigated promptly to rule out any intracranial complications. Immediate treatment of the PDPH with an epidural blood patch to prevent further CSF leakage should be considered.