The value of the 10-grade Japan Coma Scale (JCS) as a means of evaluating patients undergoing early aneurysm surgery was assessed in terms of its relationship to surgical outcome. The 13-grade Glasgow Coma Scale (GCS) was also assessed, and comparisons were made between the two. A series of 765 patients who underwent aneurysm surgery within 7 days after hemorrhage were evaluated both by JCS and GCS immediately prior to surgery, and outcome was assessed by the Glasgow Outcome Scale (GOS) 6 months postoperatively. Both the JCS and GCS scores were significantly correlated with surgical outcome (JCS vs GOS: rs = 0.586, GCS vs GOS: rs = 0.615, p < 0.001). There was no significant difference between the correlation coefficients for outcome of the JCS and GCS. In general, the better the JCS or GCS score was, the better the surgical outcome was, however, outcome among those with a JCS score of 3 was poorer than among those with a score of 10, 20, or 30. The results of this study indicate that both JCS and GCS are useful in predicting surgical outcome, but the GCS may be better than the JCS because of the problem with the score of 3 in the latter.