The purpose of this study was to investigate disability in persons with multiple sclerosis (MS) by using combinations of functional assessment scales and subscales to predict (1) the burden of care measured in minutes of assistance provided per day by another person in the home, and (2) the subject's level of satisfaction with life in general. The Functional Independence Measure (FIM), Incapacity Status Scale, Environmental Status Scale, and the Barthel Index had high intercorrelations with each other. Although each was predictive of the MS subject's physical care needs, the FIM was the most useful. A change in total FIM score of one point was equivalent to an average of 3.38 minutes of help from another person per day. With the Brief Symptom Inventory and the Environmental Status Scale, the FIM contributed to predicting the patient's general satisfaction as well. We propose that burden of care and subjective satisfaction with life be the standards by which functional assessment instruments are compared to reflect, in pragmatic terms, the impact of disability on the lives of individuals and on the human and economic resources of the community.