High-resolution magnetic resonance imaging (HRMRI) has a unique ability to provide an evaluation of the intracranial artery wall. This study aimed to investigate the possible mechanisms of ischemic stroke in patients with intracranial atherosclerosis using HRMRI. HRMRI was performed on 55 patients (38 male and 17 female) with acute cerebral infarction to investigate the lumen-intruding plaque at the stenotic portion of the middle cerebral artery (MCA) and basilar artery (BA) and to attempt to identify the mechanisms of stroke. Penetrating artery disease (PAD) was diagnosed in 20 patients (36%) and large-artery atherosclerosis (LAA) was diagnosed in 35 patients, including 19 with parent artery plaques occluding a penetrating artery (POPA; 35%) and 16 with artery-to-artery embolisms (29%). Patients with PAD had a higher frequency of hypertension compared with that of the patients with LAA (80 versus 29%; P<0.001), and patients with LAA had a higher frequency of diabetes compared with that of the patients with PAD (40% versus 15%; P=0.054). Magnetic resonance angiography revealed mild to moderate stenosis in the patients with POPA, while border zone infarction and artery-to-artery embolism occurred in the majority of the patients with severe stenosis or occlusion of the MCA and BA. HRMRI has the ability to identify the mechanisms of intracranial atherosclerotic ischemic stroke through the detection of luminal plaques.