We can not necessarily find sufficient reports that investigate the pathophysiology and the clinical course of the subacute subdural hemorrhage (SASDH). In other words, this state is a relatively rare pathology and the origin, mechanism of occurrence, clinical course and prognosis have not analyzed yet in detail. Now, we have experienced a rare case who suffers from the acute subdural hematoma (ASDH) after the head trauma. Then, after the conservative treatments, the rapid growth of the volume of the hematoma with radiographical irregularity by computed tomography (CT) has identified in subacute stage (about one month after). In addition, this patient manifested neurological deterioration, mainly consciousness disturbance resulting in the aspiration pneumonia which may be the fatal cause. Therefore, we performed chemotherapy (administration of antibiotics) without the hyperalimentation such as tube nutritional support or intravenous hyperalimentation. Fortunately, the presented case has showed the slight shift of midline structure, not but the compression to midbrain by the uncal gyrus, the disappearance of the ipsilateral ambient cistern as the signs of intracranial herniation. In addition, he was marked elderly. So, operation (craniectomy, evacuation of the subdural hematoma and the external decompression) was not performed but the conservative therapy. In the subacute stage (one month later), since the hematoma has grown rapidly with radiographical irregularity (mixture of high density and low one) as described above, we performed the operation (perforation and drainage). However, His neurological improvement (mainly recovering from the consciousness disturbance) has not obtained. Therefore, we have investigated the relatively rare reports concerning the pathophysiology of the SASDH. Even if the signs of the uncal herniation that deteriorate the prognosis of the patients suffering from SASDH has not identified, the presented case of this disorder would suffer from systemic complication such as a swallowing disturbance and an eating difficulties resulting in the serious aspiration pneumonia because of the decreasing elastance of the brain after the disappearance of the hematoma. Even if the volume of the brain recover, it is suggested that the cerebral blood flow would not decrease compared with it before the trauma.