Background. Little work has been published on the internal structure of the Mini-Mental State Examination (MMSE), one of the most widely used instruments for grading cognitive status in clinical settings and field research.

Methods. MMSE responses from a sample of older adults (50–98 years) in five US sites (N = 8556) were analysed.

Results. A five-factor solution was found to be most appropriate. The first factor (concentration) had large loadings with serial sevens and spell world backwards items. The second factor (language and praxis) had large loadings with naming, follow command and praxis items. The third factor (orientation) had loadings with orientation to time and place items. The fourth factor (memory) had large loadings with delayed recall items and the fifth (attention) had large loadings with immediate registration items.

Conclusions. We found that the MMSE is essentially unidimensional; nevertheless, evidence was revealed suggesting that the MMSE is a multidimensional assessment instrument. Dimensions revealed in this sample correspond directly to MMSE sections articulated by the developers of the instrument. These findings have not been reported in previous factor analyses of the MMSE. The findings support the construct validity of the MMSE as a measure of cognitive mental state among community dwelling older adults.