Although the Blessed Dementia Rating Scale (BDRS), a clinical screening instrument, has been applied extensively, no suitable cut-off values and clinical application have been proposed, particularly in mild cognitive impairment (MCI), the precursor of dementia. The BDRS, Mini Mental State Examination (MMSE), and Clinical Dementia Rating Scale (CDR) were administrated in people aged 65 years and above, who were enrolled from southern Taiwan with multistep stratified random sampling and followed-up for 2 years. All subjects (total number = 3,027), with new onset of MCI (defined as CDR = 0.5) in the first year and dementia (defined as CDR > or = 1) in the second and third years were subjected to statistical analysis. In distinguishing normal from MCI, except in the literate group aged 65-74 years, MMSE was superior to BDRS, with cut-off values of 1 in both literate groups aged 65-74 years and > or = 75 years, and 1.5 and 2 in less educated groups aged 65-74 and > or = 75 years, respectively. In distinguishing MCI from dementia, BDRS had cut-off values of 2.5 in both literate groups aged 65-74 and > or = 75 years, and 2.5 and 3 in less educated groups aged 65-74 and > or = 75 years, respectively. These values were better than those for MMSE in all groups. BDRS might be considered as a better tool than MMSE to screen for MCI and dementia in the increasing proportion of literate elderly aged 65-74 years in the aging population.