Intraoperative rupture of an intracranial arterial aneurysm can dramatically interrupt a deliberate microsurgical procedure and jeopardize the patient's chances for a favorable outcome. Intraoperative rupture occurred in 58 of 307 (19%) consecutive aneurysm procedures done at The University of Texas Health Science Center. Rupture occurred during three specific periods: early or predissection in 7%, dissection in 48%, and clip application in 45%. Outcome after rupture during the predissection interval was poor, with only 1 of 4 patients surviving. Aneurysmal rupture during dissection could be attributed to blunt dissection techniques in 75% of the cases and to sharp subarachnoid dissection in 25%. The outcome was favorable in only 50% of the patients sustaining blunt dissection errors, whereas all patients sustaining intraoperative rupture during sharp dissection recovered well. Rupture during clip application was attributed to incomplete dissection in 65%, poor clip application in 31%, and a mechanical clip failure in 1 case. Eighty-eight per cent of the patients who underwent uneventful operative procedures had favorable outcomes, whereas only 62% of the patients suffering intraoperative rupture recovered well. The use of sharp microsurgical techniques with a systematic contingency plan for dealing with sudden hemorrhage and the judicious use of temporary clips should minimize the adverse effect of intraoperative rupture on overall management morbidity and mortality.