Apolipoprotein C-III (apoC-III) is the major component of triglyceride-rich lipoproteins. One of six identified polymorphisms in the apoC-III 5'-untranslated region (T-455C) is located within a functional insulin-response element. In a group of 137 elderly individuals (70-106 years old), the allele distribution was analyzed using restriction fragment length polymorphisms. Statistical analysis of allele frequencies was performed on subgroups selected by age and in elderly patients with arterial hypertension or ischemic heart disease. A greater frequency of the apoC-III -455C allele was demonstrated with aging (p < .005). No statistically significant difference in allele distributions was detected between healthy subjects and groups of elderly patients of the same age with either ischemic heart disease or arterial hypertension. The increased incidence of the C allele with advanced age indicates that this variant promoter is associated with longevity. The greater incidence of this allele is detectable only in adults older than 80 years of age.