OBJECTIVES: Multiple sclerosis (MS) is a chronic progressive neurologic disease and one of the most common causes of disability among young adults. Although the clinical manifestations and symptoms of MS are diverse, disease severity is generally measured by ambulation based Expanded Disease Severity Scale (EDSS). While EDSS captures well the level of disability due to the involvement of lower extremities and urinary bladder, its ability to capture other aspects such as fatigue and mental function are poor. The aim of this study was to explore the relationship between two patient-based measures, a self-administered EDSS and Multiple Sclerosis Impact Scale (MSIS-29), a psychometrically validated instrument measuring the physical (20 items) and psychological (nine items) impact of MS. METHODS: In total, 553 Finnish persons with MS (PwMS) drawn from the membership register of the national patient association completed a postal survey, including EDSS and MSIS-29. RESULTS: PwMS at every (0-9) impairment level of the EDSS scale were represented. The mean EDSS score was 4.0, indicating moderate disability. The physical impact of MS was strongly related to disease severity, with the scores ranging from 3.0 in the mildest disease (EDSS 0) to 76.2 in the most severe disease (EDSS 8 – 9). The psychological impact increased synchronously with the EDSS score in mild disease (EDSS 0 - 3) and peaked at EDSS 5, declining thereafter from EDSS 5 to 7. In most severe disability (EDSS 8 – 9) the psychological impact of MS was equally high as in EDSS 4. CONCLUSIONS: The subjective physical burden of MS increases steadily with self-assessed disease severity, whereas the psychological burden does not go hand in hand with the self-assessed severity of the disease.