During 1980-85, cerebral angiography was performed as soon as possible for early operation of ruptured aneurysms. However, during that period, the incidence of rebleeding during angiography conducted within 6 hours after the initial rupture was approximately two-fold higher than the rate of rebleeding within 6 hours for the total series. Therefore, since 1986, patients with grades I-IV have been managed with complete bed rest, and angiography has been withheld during the first 6 hours after rupture, except in patients in whom emergency operation was anticipated. To investigate whether this change of policy has been effective in decreasing ultra-early rebleeding within 6 hours after rupture, patients admitted during 1986-92 were compared with those admitted during 1980-85. Of the total 418 patients who were admitted within 6 hours after initial rupture, 61 (15%) had ultra-early rebleeding: 18 prior to and 43 after admission. The rebleeding rate during angiography within 6 hours after rupture was 7%. In patients with grades I-IV, the percentage of patients receiving angiography within 6 hours after rupture decreased from 45% during 1980-85 to 13% during 1986-92 (p < 0.01), and the ultra-early rebleeding rate decreased from 15% during 1980-85 to 5% during 1986-92 (p < 0.01). However, with the increase in number of patients referred in the ultra-early stage, the number of rebleeding cases during transfer increased. In conclusion, in order to reduce the rate of ultra-early rebleeding, withholding aggressive management such as angiography in this stage seems to be effective, and if there is no need for emergency operation, it is better to withhold patients' transfer in this stage and commence it soon after 6 hours following subarachnoid hemorrhage.