Intracranial stenosis due to atherosclerosis is a disease of significant prevalence worldwide and is responsible for a significant economic burden due to stroke-related disability. Known risk factors including age, race, sex, and medical co-morbidities contribute to its incidence. While ischemic stroke and transient ischemic attack can develop from myriad mechanisms in patients with intracranial stenosis, it is likely that an interplay of hemodynamic failure, in-situ thrombosis, and distal embolism results in brain ischemia. Knowledge of disease prevalence, risk factors, and pathophysiology is critical to development of better medical and interventional treatments for this grave condition.