Fatigue is a frequent symptom of multiple sclerosis (MS). It has been reported to varying degrees at all stages of the disease by 50 to 90% of all MS patients. Fatigue is now recognised as a disabling symptom which negatively impacts daily living. This symptom was underrated until recently but has now been included in clinical practice. Most fatigue scales have been developed in the English language and are culturally specific to their country of origin. The Fatigue Severity Scale is a one-dimensional nine-item scale which briefly assesses the impact of fatigue on the daily lives of MS patients. It has been widely used in different studies, even though it appears to be less relevant than the multi-dimensional 40-item Fatigue Impact Scale which was developed in Canada by Fisk et al (1994). The Fatigue Impact Scale is useful because it assesses different aspects of MS-related fatigue, such as the effects of fatigue on cognitive and physical activities and can include daily living. The Multiple Sclerosis Council for Clinical Practice Guidelines recommends the use of a 21-item Modified Fatigue Impact Scale which is a shortened version of the 40-item Fatigue Impact Scale. Using word-for-word translations of these scales into French would fail because the results would not be interpretable. We first translated and culturally adapted the Fatigue Impact Scale to French-speaking patients. We then evaluated the psychometric properties of this French version (EMIF-SEP). We used the EMIF-SEP scale to study fatigue in French MS patients. We found a significant correlation between higher EMIF-SEP total scores and higher EDSS scores; likewise physical dimension of the EMIF-SEP were linked to disability. But no correlations were found between the cognitive aspects of fatigue and disability. Other studies have failed to show any correlation between fatigue and disability. We suggest that this may be due to differences in sample size, or to the type of instrument used to quantify fatigue. As seen above, some tools do not allow for multi-dimensional assessment of fatigue. The EMIF-SEP scale is useful in that it allows for qualitative and quantitative assessment of fatigue.