Cognitive impairment is highly prevalent among the elderly. Subjects with disturbed glucose metabolism may be at risk of impaired cognitive function, as these disturbances can influence cognition through atherosclerosis, thrombosis and hypertension. We therefore studied the cross-sectional association of cognitive function with hyperinsulinaemia, impaired glucose tolerance and diabetes mellitus in a population-based cohort of 462 men aged 69 to 89 years. Cognitive function was measured by the 30-point Mini-Mental State Examination. Results were expressed as the rate ratio (95% confidence interval) of the number of erroneous answers given on the Mini-Mental State Examination by the index compared to the reference group. Compared to subjects with normal glucose tolerance, known diabetic patients had a rate ratio of 1.23 (1.04-1.46), newly-diagnosed diabetic patients of 1.16 (0.91-1.48) and subjects with impaired glucose tolerance of 1.18 (0.98-1.41), after adjustment for confounding due to age, occupation and cigarette smoking (p-trend = 0.01). Non-diabetic subjects in the highest compared to the lowest quartile of the area under the insulin curve had a rate ratio of 1.24 (1.03-1.50), after adjustment for confounding (p-trend = 0.02). The results did not change appreciably when potentially mediating factors, including cardiovascular diseases and risk factors associated with the insulin resistance syndrome, were taken into account. These results suggest that diabetes, as well as impaired glucose tolerance and hyperinsulinaemia in non-diabetic subjects are associated with cognitive impairment.