OBJECTIVES: To investigate the resources used by ischemic stroke patients when hospitalized, and examine this relationship by stroke severity. Comparing a bottom-up costing approach with national top-down costs. METHODS: Data from five Belgian hospitals were requested for the years 2008 up to 2011 detailing the length-of-stay (LOS), drugs, medical imaging and clinical biology tests. Participating hospitals were distributed across the country and included regional as well as teaching hospitals. Severity of the stroke was defined as mild, moderate, major or severe according to the Severity-of-Illness (SOI) categorization within APR-DRG category 045, which is determined by the classification of primary and secondary diagnoses. Average bottom-up costs were compared to the national reimbursement received by hospitals. RESULTS: