The bedside and office assessment of cognitive abilities in moderately to severely impaired patients with Alzheimer disease could be enhanced by a well-standardized instrument. The authors' group has developed such an instrument (i.e., Severe Mini-Mental State Examination; SMMSE) to assess this population. Based on the Folstein Mini-Mental State Examination (MMSE), the SMMSE, which totals 30 points, was designed to briefly assess cognitive domains relatively preserved in moderate to severe Alzheimer disease. One hundred eighty-two patients with possible or probable Alzheimer disease were administered both the MMSE and SMMSE. Performances on the SMMSE and MMSE were found to correlate significantly only when MMSE fell below 9 points (p < 0.0001). However, as performance on the MMSE approached floor levels, patients continued to score at half maximal levels on the SMMSE. Functional staging with the Clinical Dementia Rating Scale and the Global Deterioration Scale also were found to significantly correlate with performance on the SMMSE (p < 0.001). Test-retest performance on both the SMMSE and MMSE was relatively stable over a period of 5 months. Inter-rater reliability of the SMMSE was excellent. These results suggest that the SMMSE has both construct and criterion validity for assessing severely impaired Alzheimer disease patients. Our results also suggest that the SMMSE may be a useful instrument for assessing severely impaired patients at the bedside and in the office.