The purpose of this study was to examine the relationships between severity of disability and factors such as rehabilitation fees, length of stay and efficiency for hospitalized stroke patients. One hundred and seven first-time stroke patients were studied consecutively for this study. They were recruited from a rehabilitation ward in a university medical center during 1997. Functional ability was evaluated using the Functional Independence Measure (FIM) instrument on admission and discharge. Stroke patients who presented with similar degrees of disability were put together using the admission FIM score (FIM Function-Related Groups, FIM-FRGs) for further analysis. Twenty-eight (26.2%) patients examined were categorized as severely disabled (scored 18-36), 48 (44.8%) moderately disabled (scored 37-72) and 31 (29.0%) mildly disabled (scored 73-126). The average expense on rehabilitation fees, for the average rehabilitation length of stay (LOSR) of 34.7+/-16.7 days, was NT $27,645+/-13,812. The FIM score improved from 56.8+/-24.2 on admission to 76.6+/-26.2 at discharge, with a rehabilitation efficiency index (EIR) of 0.7+/-0.7. Further analysis indicated that there were significant differences among the three disability groups on rehabilitation fees and LOSR while EIR was unaffected. The findings of this study suggest that FIM-FRGs can differentiate different rehabilitation needs in terms of rehabilitation fees and LOSR; therefore, a prospective case payment system based on FIM-FRGs is suggested for stroke rehabilitation reimbursement scheme in the future.