It was hypothesized that blood pressure would be inversely related to cognitive functioning, if unconfounded with antihypertensive medication and measured over many occasions prior to neuropsychological testing. For stroke-free Framingham Study participants aged 55-88 years (n = 1,702), blood pressure levels were averaged over five biennial examinations (1956-1964) when few hypertensives were being treated, and examined in relation to neuropsychological tests administered between 1976 and 1978. With age, education, occupation, cigarette smoking, alcohol consumption, and gender controlled, blood pressure levels and chronicity of hypertension were inversely related to the composite score and measures of attention and memory. This was true for the full sample, for a subsample untreated during blood pressure measurement (n = 1,485), and for a subsample untreated throughout the entire study period (n = 1,038). For example, decline per 10 mmHg increment in blood pressure ranged from -0.04 to -0.07 standard score units (z) for the composite score. A negative finding previously was most likely due to blood pressure measurement concurrently with neuropsychological testing, or too few measurements. Hypertension-associated pathogenic processes may cause mild cognitive impairment, but other mechanisms need to be considered.