We report a case of intracerebral pneumocephalus following a head injury. This condition is relatively rare, and only 14 cases, including the present case, have been reported to data. A 40-year-old man fell from a 3rd floor window on June 29, 1999. The patient was admitted to the hospital. Plain skull X-ray films revealed a left basal skull fracture, and CT scan revealed a small contusion at the left frontobasal lobe. The patient was treated conservatively. On July 16, he underwent an MRI, and a small contusion was revealed at the left frontobasal lobe. In addition, the brain appeared to have herniated into the ethmoidal sinus. On July 22, the patient underwent a CT scan, and a intracerebral pneumocephalus was revealed in the left frontal lobe. On August 2, an MRI was performed, and intracerebral pneumocephalus in the left frontal lobe and herniation of the brain into the ethmoidal sinus were noted. In addition, intracerebral pneumocephalus had increased. The patient was admitted to our hospital. Clinotherapy was performed, but intracerebral pneumocephalus increased. On August 9, the patient underwent surgery to repair the skull base. During surgery, it was noted that the left frontal contusion had adhered to the edge of the lacerated dura around the bone defect of the ethmoidal sinus. Following surgery, no recurrence of pneumocephalus was noted. We conclude that once intracerebral air volume increases, early surgical repair should be carried out for intracerebral pneumocephalus. Meticulous MRI investigations of the lesion causing the intracerebral pneumocephalus should be conducted to select an appropriate operative procedure.