Research directed towards early diagnosis and therapy of dementia demands rapid identification of prodromal mild cognitive impairment (MCI). A longitudinal study was designed to clarify whether different domains of cognitive impairment, tested by Mini-Mental State Examination (MMSE), help predict dementia. After 3.74+/-2.94 years of follow-up among 291 cognitively normative volunteers, 73 developed MCI. During the next 3.88+/-3.01 years of MCI follow-up, 47.9% of MCI developed dementia of Alzheimer's type (DAT), 20.5% of MCI developed vascular dementia (VaD) and 31.5% maintained persistent MCI at the time of data analysis. Total MMSE and subtest scores analyzed at MCI onset showed significant differences for serial seven subtest scores between DAT and persistent MCI (P<0.05). Rates of change in subtests of orientation and memory and total MMSE scores predicted DAT (P<0.01). Decreasing orientation and total MMSE scores predicted VaD conversion rates of MCI to DAT at 2 years were 20.06% among single-domain MCI versus 41.7% for multi-domain MCI (P<0.05). Subjects with MCI often have impaired cognitive domains other than memory and show rapid deterioration, which predicts DAT. VaD sometimes mimics DAT with subtle cognitive impairment appearing before onset of dementia.