Decrease in cardiovascular disease mortality below age of 65 years, which has been observed in Poland since 1992, is followed by increasing number of elderly people. One of the typical problems of ageing is deterioration of cognitive function. Little is known on prevalence of cognitive impairment and its correlates in Polish population. The goal of this paper was to assess the prevalence of cognitive impairment in the elderly Polish rural population and to study the differences in the distribution of cognitive function and frequency of cognitive impairment by age, sex, education and by history of previous MI. Studied group were 943 men and women at age 65-78 from the cohort representing the population of Polish rural province (Tarnobrzeg Voivodship). Participants were visited at their homes. Interview and cognitive function assessment by Mini-Mental State Examination (MMSE) procedure were carried out according to the standard questionnaire. Participation rate was 94%--882 persons were examined. There were 58% women and 17% persons at age 75 or older in the examined group. 87% had only elementary (7 years of schooling) education or less. History of previous myocardial infarction was found in 15% of participants. In almost half of participants the result of MMSE < or = 25 points suggested cognitive impairment. More severe impairment (MMSE < or = 21 points) was found in 15% of examined persons. In participants at age 75 years or older and in those with low education, per cent of persons with cognitive impairement function was higher. Sex and history of previous myocardial infarction were not related to frequency of cognitive impairment. Results indicate the high prevalence of the cognitive impairment in elderly men and women in Polish rural population with low average level of education.