Blood coagulation capacity increases with age in healthy individuals. Through extensive Longitudinal analyses of human factor IX gene expression in transgenic mice, two essential age-regulatory elements, AE5' and AE3', have been identified. These elements are required and together are sufficient for normal age regulation of factor IX expression. AE5', a PEA-3 related element present in the 5' upstream region of the gene encoding factor IX, is responsible for age-stable expression of the gene. AE3', in the middle of the 3' untranslated region, is responsible for age-associated elevation in messenger RNA Levels. In a concerted manner, AE5' and AE3' recapitulate natural patterns of the advancing age-associated increase in factor IX gene expression.