INTRODUCTION: Intracranial large artery atherosclerosis (ICAS) is a common cause of stroke in Asia. Prior epidemiological publications on ICAS have largely been single-country reports. This collaborative study involving several Asian countries aims to investigate the characteristics and outcomes of patients with stroke attributable to ICAS. METHODS: This is an international, multicenter, observational, prospective cohort study of patients admitted with acute ischemic stroke secondary to ICAS to stroke centers in six Asian countries. Stroke due to ICAS was diagnosed when there was a ≥50% intracranial large artery stenosis ipslateral to a non-lacunar infarct, without significant ipsilateral extracranial stenosis, cardiac cause or other mechanism found for the stroke. Data were collected on patient demographics, vascular risk factors, stroke location, and severity. Outcomes of interest were stroke recurrence and mortality at 12-month follow-up. RESULTS: A total of 356 patients were recruited. Mean age was 62.7 ± 13.8 years, and 39.9% were females. Mean NIHSS on admission was 9 ± 8, with majority of patients having mild (39.3%) or moderate (37.9%) strokes. Stroke recurrence was 6.7% (95% CI: 4.4-9.9%) while mortality rate was 13.2% (95% CI: 9.9-17.2%) within 1 year. The risk of stroke recurrence was associated with increasing age (odds ratio [OR]: 1.04, 95% CI: 1-1.06, p = 0.05) and hypertension (OR: 3.23, 95% CI: 1.09-9.61, p = 0.035). Mortality was associated with age (OR: 1.05, 95% CI: 1.01-1.08, p = 0.006) and NIHSS (OR: 1.12, 95% CI: 1.07-1.17, p <
0.001). CONCLUSIONS: This multicenter Asian study demonstrates a high risk of stroke recurrence and mortality among patients with acute stroke due to ICAS. They are associated with age (both), as well as hypertension (for recurrence) and NIHSS (for mortality). Better treatment modalities are needed to reduce the frequency of adverse outcomes in symptomatic ICAS.