The authors have analyzed the correlation between the result of early operation for ruptured intracranial aneurysms (45 cases) and CT scan (54 cases) performed within the second weeks after subarachnoid hemorrhage (SAH). 1) Twelve patients operated on within 24 hours after SAH showed no mortality and a morbidity of 16%. On the contrary, in 12 patients operated on during 2nd-7th days after SAH, the mortality rate was 38% and the morbidity 15%. 2) There was a good correlation between the result of early operation within one week after the hemorrhage and CT findings. Surgical results were closely correlated to the incidence of vasospasm in our cases. All cases with symptomatic vasospasm showed bilateral high density in the cistern or ventricles on CT scan performed within 3 days after initial bleeding. 3) In the cases of ruptured aneurysm with giant intracranial hematoma, but no remarkable blood clot in ventricles or basal cisterns, the results of surgery in acute stage were good. 4) For the cases within 24 hours after the hemorrhage, it is recommended to carry out surgical operation as early as possible, including removal of blood clots in the basal cistern and sylvian fissure, and ventriculo-cisternal drainage for improvement of cerebrospinal fluid (CSF) circulation. On the other hand, the cases in which operations were performed during 2nd-7th days and CT scan revealed bilateral high density in the cisterns or ventricles resulted in poor outcome or death.