The relation between hypertension and cognitive function is not well established. Therefore, we examined cognitive function in a random sample of 744 nondiabetic elderly inhabitants of Kuopio, East Finland. Five brief neuropsychological tests known to be sensitive to cognitive impairment due to dementia – the Mini-Mental State Examination (MMSE), the Trail Making Test (TMT), the Buschke Selective Reminding Test (BSR), Russell's Adaptation of the Visual Reproduction Test (HVR), and the Verbal Fluency Test (VFT) –were used to evaluate cognitive function. The performance of the hypertensive group (n=378) was impaired in almost all test items compared with that of the normotensive group (n=366), but the difference between these two groups was statistically significant in 5 of 19 test items only. Moreover, within the hypertensive group, hyperinsulinemic (fasting plasma insulin > 17.9 mU/L) hypertensive subjects (n=57) scored worse than normoinsulinemic hypertensive subjects (n=321) in 16 of 19 test items and worse than the normotensive subjects in the same 16 of 19 test items. The difference between the hyperinsulinemic hypertensive and normotensive groups was significant in 11 test items that reflected complex cognitive function such as calculation, language, semantic memory, and problem solving. This difference in neuropsychological tests among the three study groups (normotensive, normoinsulinemic hypertensive, and hyperinsulinemic hypertensive subjects) persisted after adjustment for fasting plasma glucose, age, sex, and education in 3 test items measuring calculation, copying, and semantic memory. Thus, essential hypertension in the elderly is associated with an impairment in complex cognitive function. Furthermore, hyperinsulinemia seems to identify a subgroup of hypertensive subjects with a particularly poor performance in neuropsychological tests requiring complex cognition such as semantic memory, problem solving, and abstraction.