Seven cases of traumatic subdural hygroma are presented, with discussion of their predilection in the frontal region, clinical features and postoperative course. It is shown that hygroma can be the principal or secondary cause of the frontal lobe syndrome following head trauma. None of the cases could be well differentiated from chronic subdural hematoma by angiography and CT scan. Therefore a neurosurgical intervention, such as an osteoplastic craniotomy or a simple trephination has been employed for the diagnosis and the treatment. In the operation of the chronic subdural hygroma, the arachnoid flap of it or the membrane, if it is formed, should be widely excised. After the operation continuous drainage through a cranial hole for several days would be ideal.