BACKGROUND/AIMS: Hypertension is an established risk factor for dementia. However, the association between blood pressure and cognition in the very old is not fully determined and important to study considering the ageing population and the morbidity associated with cognitive impairment. METHODS: This cross-sectional study included 575 individuals aged 85, 90 or 95 years and above and living in northern Sweden or Finland. Participants were interviewed and assessed using a structured protocol. Systolic (SBP) and diastolic blood pressures (DBP) were measured and pulse pressure (PP) calculated. Cognitive function was evaluated using the Mini-Mental State Examination (MMSE). Data were also collected from medical charts and caregivers. RESULTS: After adjustment for several demographic variables and diagnoses, SBP was significantly associated with MMSE in a nonlinear fashion; both high and low pressures were associated with poorer results. There was also a linear and positive association between PP and MMSE scores, but no association with DBP was found. Participants with dementia had lower blood pressure. CONCLUSION: After adjustment for a number of health factors, there was an association between low blood pressure and cognitive impairment. The direction of any causal relationship between blood pressure and cognition remains to be determined.