To clarify the early prediction of outcome in severe head injury patients with evacuated mass lesions, 32 patients with a Glasgow Coma Scale (GCS) score of 8 or less were classified as having a good outcome (11 cases) or a poor outcome (21 cases). The following parameters affecting the prognosis were analyzed, i,e., the patient's age and sex, type of injury, the presence of hypotension and/or hypoxia, time from injury to arrival at the emergency room and/ or operating room, the admission GCS, pupillary abnormalities, CT findings, and continuous monitoring of intracranial pressure (ICP), cerebral perfusion pressure (CPP) and jugular venous oxygen saturation (SjO2) for 1-5 days after the injury. The patient's age, the admission GCS score, ICP on day 1 after the injury, and CPP on day 0 after injury were powerful factors that affected the prognosis. Other parameters showed little difference between the two groups. However, the presence of hypotension and/or hypoxia showed a tendency for poorer outcomes, and episodes of jugular venous desaturation (SjO2<50%) were common during the initial 3 days in the poor outcome group. These results suggest that the first prognostic evaluation can be performed after 3 days by considering primary and secondary brain damage. (JJAAM 1998; 9: 95-101)