We observed the decline in cognitive functioning in a community cohort of 924 persons aged > or =75 years with initially good cognition. Cognitive performance was indexed with the Mini-Mental State Examination (MMSE) on two occasions, 3 years apart. The average decline in MMSE score was 0.4 points per year. However, 23.4% of the participants lost more than 10% of their baseline MMSE scores. Women declined more rapidly than men. Baseline advanced age, lower education, and stroke predicted the greater decline in women. It appears that the relation of lower education and stroke with cognitive decline was more pronounced in men, but age did not predict cognitive decline in men. In addition, there was a correlation between systolic pressure reduction and cognitive decline in women, which was not accounted for by other factors. In summary, although the cognitive ability is generally spared longitudinally, in terms of the entire population, a considerable proportion of individuals show substantial decline that is related to several factors such as advanced age, female gender, lower education, stroke, and systolic pressure reduction.