Criterion-referenced (Livingston) and norm-referenced (Gilmer-Feldt) techniques were used to measure the internal consistency reliability of Folsteins Mini-Mental State Examination (MMSE) on a large sample (N = 418) of elderly medical patients. Two administration and scoring variants of the MMSE Attention and Calculation section (Serial 7s only and WORLD only) were investigated. Livingston reliability coefficients (rs) were calculated for a wide range of cutoff scores. As necessary for the calculation of the Gilmer-Feldt r, a factor analysis showed that the MMSE measures three cognitive domains. Livingstons' r for the most widely used MMSE cutoff score of 24 was .803 for Serial 7s and .795 for WORLD. The Gilmer-Feldt internal consistency reliability coefficient was .764 for Serial 7s and .747 for WORLD. Item analysis showed that nearly all of the MMSE items were good discriminators, but 12 were too easy. True score confidence intervals should be applied when interpreting MMSE test scores.