Although a number of standard scales exist for the assessment of the mildly to moderately demented patient, measurement of cognitive decline needs to be extended beyond this stage and into the range of functioning characteristic of the severely impaired individual. To do this, assessment techniques need to be developed which take into account the specific behavioral and cognitive deficits seen in severe dementia. Until such techniques are developed. a full and adequate account of the natural history of cognitive decline in AD is not possible. We have introduced a new assessment device, the Severe Impairment Battery, which evaluates a range of cognitive functioning in patients who are unable to complete standard neuropsychological tests. Preliminary results with this test are encouraging and suggest that, contrary to popular belief, many severely cognitively impaired patients are testable if appropriate techniques and strategies are applied.