The purpose of our study was to evaluate the outcomes of neurosurgical and endovascular treatment of ruptured intracranial aneurysms over a lifetime, based on the results of the International Subarachnoid Aneurysm Trial. We performed a decision analysis, using a Markov model, to evaluate outcomes of neurosurgical and endovascular treatment of ruptured intracranial aneurysms that were suitable for both treatments over a lifetime. We chose 50 years as cohort age. Effectiveness was measured in quality-adjusted life-years (QALYs). In addition, we calculated life expectancy and subarachnoid haemorrhage (SAH)-related mortality and disability rates. Compared with neurosurgery, endovascular treatment increased effectiveness by 1.0 QALY (neurosurgery, 13.1 QALYs; endovascular treatment, 14.1 QALYs) and life expectancy by 0.7 years (neurosurgery, 23.2 years; endovascular treatment, 23.9 years), and decreased SAH-related mortality by 0.4% (neurosurgery, 11.5%; endovascular treatment, 11.1%) and SAH-related disability by 5.0% (neurosurgery, 21.3%; endovascular treatment, 16.3%). One-way sensitivity analysis showed that no parameters influenced the effectiveness of endovascular treatment compared with neurosurgery. For ruptured intracranial aneurysms suitable to both neurosurgical and endovascular treatment, endovascular treatment is more effective than neurosurgery over a lifetime.