BACKGROUND : Intracranial atherosclerotic disease (ICAD) is a major cause of stroke worldwide. The optimal management of patients with symptomatic ICAD is controversial. Therefore, the aim of this systematic review is to compare medical management versus surgical bypass for the treatment of symptomatic ICAD. METHODS : A literature review was performed to identify studies reporting outcomes of patients with ICAD who were managed medically or surgically with either direct or indirect bypass. Baseline, treatment, and outcomes data were analyzed. Complications included ischemic stroke, intracranial hemorrhage, and cerebrovascular death. Secondary analyses of the surgically treated cohort were performed to compare the outcomes of direct versus indirect bypass. RESULTS : The pooled analysis was derived from 18 studies, comprising a total of 2160 patients with ICAD, including 1790 managed medically and 370 treated with surgical bypass. The rates of ischemic stroke, intracranial hemorrhage, and cerebrovascular death were 16%, 1%, and 4.5% in the medical cohort, respectively, versus 8%, 0.6%, and 1.9% in the surgical cohort, respectively. Among patients with ICAD who underwent bypass surgery, the rates of ischemic stroke and cerebrovascular death were 7% and 1.9% in the direct bypass group, respectively, versus 19% and 2.1% in the indirect bypass group, respectively. CONCLUSIONS : Direct or indirect bypass surgery is a reasonable treatment option for appropriately selected patients with ICAD. Careful preoperative evaluation of hemodynamic parameters and the relevant donor and recipient vessels is crucial to maximizing the success of bypass for ICAD. Further studies remain necessary to clarify the roles of medical versus surgical management for ICAD.