Background: Intracranial atherosclerotic disease is the most common cause of ischemical cerebrovascular events. The risk of stroke recurrence or death of ICAD patients remains very high. Previous nonrandomized studies have showed that stroke and death rate of angioplasty for ICAD patients with severe stenosis of intracranial artery is lower than that of aggressive medication. Methods: The trial is a multicenter, prospective, randomized, parallel controlled study, with the primary idea to determine whether intracranial balloon angioplasty combined with aggressive medical therapy is superior to aggressive medical treatment alone in patients with cerebral ischemic stroke due to neurovascular stenosis (≥70%) for preventing the primary endpoint: 1.Stroke (including hemorrhagic and ischemic stroke) and all-cause mortality within 30 days after enrollment. 2. Ischemic stroke attributed to the offending vessel from 31 days to 12 months after enrollment. Aggressive medical treatment is identical in both arms, which consists of aspirin 100 mg per day during the entire follow-up and clopidogrel 75mg per day for the first 90 days after enrollment. Management of primary risk factors (blood pressure 130-140 / 90-100 mmHg and LDL < 70 mg/dl) and secondary risk factors is also required in both arms. Result: We postulate that balloon angioplasty with submaximal balloon is safe enough and effective enough, not increasing ischemic/hemorrhagic stroke rate within 30 days. Moreover, we expect primary angioplasty combined with optimal medical management can reduce a relatively 50% risk of recurrent ischemic stroke due to attributed artery with estimated rate of 15% at 1 year in the control group and 7% in the treatment group in 1-year follow-up. Conclusion: BASIS is the first randomized trial comparing primary angioplasty combined with optimal medical regime with optimal medical regime alone. With enough evidence, we believe the risk of major hemorrhage can also be maximal minimized by using submaximal balloon during the procedure and probably shorter-term dual antiplatelet treatment after procedure. With the result of BASIS, we hope primary angioplasty can serve as an independent or alternative treatment in patients with severe intracranial atherosclerotic stenosis