During the period from June, 1961 to September, 1975, 1080 cases of intracranial saccular aneurysms were experienced in Tohoku University. This investigation is based on the follow-up studies of 59 cases which were treated conservatively. On discharge the condition of the cases were classified into the following 5 groups: "Excellent", the patients is fully capable for employment, "Good", the patient is capable of working, although some neurological deficits remain, "Fair", the patient has one or more of three handicaps--Incapability of walking independently, psychic disturbances or aphasia, "Poor", the patient is completely incapable of walking even with assistance. The results of 59 cases were evaluated on discharge. The total consisted of 15 excellent cases, 2 good, 2 fair, 2 poor and 38 deaths. The follow up studies were obtained from the all cases which were discharged from the hospital (the follow up rate of 100%). The follow-up periods ranged from six months in minimum to 11 years and 9 months in maximum with the average periods of 3 years and 6 months. The results on follow up studies revealed 13 excellent cases, 0 good, 0 fair, 0 poor, and 8 deaths. Six cases out of 13 which were reported as excellent were unruputured cases. The causes of deaths were attributed to rebleeding in 3, progressive deterioration associated with rupture of aneurysm in 2, neoplasma in 1, acute abdomen in 1, and uncertain cause in 1.