A meta-analysis of the literature on morbidity and mortality from elective surgery for asymptomatic unruptured intracranial aneurysms was performed to obtain a more precise, accurate, and generalizable estimate of operative risk than is currently available. The authors used a MEDLINE search from 1966 to 1992, supplemented with manual searches, to locate studies containing four or more patients who had undergone elective surgery for these aneurysms. Only patients with asymptomatic, unruptured aneurysms were eligible for inclusion. Demographic and clinical data were collected from each series; aneurysms were categorized as incidental, multiple, or unclassifiable. Data were analyzed using Fisher's exact test and logistical regression. There were twenty-eight articles containing data on 733 patients who met eligibility criteria. The mean patient age was 48.6 +/- 5.5 years, and 55% +/- 17% of the patients were women. There was a total of 30 deficits for a morbidity rate of 4.1% (95% confidence interval 2.8, 5.8%) and a total of seven deaths for a mortality rate of 1.0% (95% confidence interval 0.4, 2.0%). There was insufficient statistical power to detect a difference in morbidity or mortality rates related to study size, year of publication, or potential risk factors such as patient sex or age, or aneurysm size, location, or category (incidental, multiple, or unclassifiable) (for all analyses, p > or = 0.16). Elective surgery for asymptomatic unruptured intracranial aneurysms, as reported in the literature, has low rates of morbidity (4.1%) and mortality (1.0%). At present there is insufficient detail in the literature to understand the impact of patient and aneurysm characteristics on elective surgical outcomes.