BACKGROUND: The frequency of acute large vessel occlusions in relation to clinical severity has not yet been established in a comprehensive, consecutive and unselected cohort of patients with hyper-acute cerebral ischemia. AIM: The aim of this study was to establish the frequency of acute large vessel occlusions and describe the relations to the National Institutes of Health Stroke Scale (NIHSS), lesion site and time from symptom onset in unselected consecutive patients with hyper-acute cerebral ischemia. METHODS: A prospective single hospital registry was based on consecutive unselected patients admitted from July 2009 to December 2011 with symptoms of acute cerebral ischemia within 4.5 h from symptom onset. ICA, M1, M2, ACA, PCA, BA and VA were assed for occlusions. Best NIHSS-cut-off values were calculated based on sensitivity and specificity for detecting any, anterior and posterior occlusions and the effect of time after symptom onset was assessed. RESULTS: Six hundred thirty-seven patients, with admission NIHSS: 1-42, were included; 183 patients presented with acute vessel occlusions (28.7%) in 15 different combinations of occlusions. The best NIHSS-cut-off for detecting any occlusion was 6. NIHSS is highly depending on lesion site, highest values being observed in relation to combined and M1 occlusions. CONCLUSION: Acute vessel occlusions are frequent in unselected patients. Occlusions occurred in all NIHSS score values but a NIHSS cut-off value of 6 most optimally predicted acute vessel occlusion, even though accuracy was low.