One hundred and sixty-eight men who were participants in the study "Men born in 1914" had their blood pressure and cognitive function examined when they were 68 years old. They were then re-examined at the age of 81. Decline on five standardized cognitive tests at the age of 81 years was studied in relation to four levels of baseline blood pressure at the age of 68. Results from multivariate analyses suggested that blood pressure, when studied in conjunction with other factors related to cognitive function, contribute to a rather modest extent and not unambiguously to the variability in cognitive decline. When decline on each separate test had been combined into a composite measure, where equal weight had been given to memory, crystallized and fluid abilities, it was shown that hypertension stage 2 (SBP 160-179 mmHg or DBP 100-109 mmHg) was associated with greater levels of overall decline. Hypertension stage 3 (SBP > or =180 mmHg or DBP > or =110 mmHg), on the other hand, was associated with lower levels of overall decline. Depressive symptoms at follow-up had a negative effect on cognitive levels and were discussed as potential confounders of hypertension-related cerebral lesions.