Until recently, severe dementia has received little attention on the part of clinicians and researchers. Yet, it represents a major problem from the point of view of Public Health because it is always accompanied by marked functional impairment with, in addition, frequent psychiatric and behavioural problems. These deficits are associated with impairment in activities of daily living that result in marked loss of autonomy and lead inevitably to the need to seek outside assistance, at least on a part-time basis. The arrival of new drugs with a potential to palliate some of the symptoms makes the assessment of severe dementia even more important. The Severe Impairment Battery (SIB) has been proposed in 1990 in order to evaluate the cognitive abilities of patients for whom standard cognitive measures are no longer adapted. Its purpose was to analyze different cognitive domains, based on the residual capacities of these patients. It evaluates the following domains: social interaction, orientation, attention, language, memory, praxis, constructional abilities and visuo spatial functions. The original SIB consisted of 51 items with a maximum score of 152. The battery was later shortened with a score of 133 and later 100. The latter version, which included 40 items, has been validated and published in France by Boller et al. However, clinical experience suggests that even this version is too long and includes some redundancies. We have therefore prepared an abridged version, which only includes 26 items with a maximum score of 50. It can be administered in 10 to 15 minutes. The selection was based mainly on clinical experience. We wanted to keep all of the domains included in the original version. Finally the selection was justified by a factorial analysis. The present version is based on a consensus reached by an US and Italian research group, in addition to ours.